Hagia Sophia, known by different names like Ayasofya in Turkish, was built a long time ago in Istanbul. Its name means ‘Holy Wisdom’. It is a very important building in history.

This building was first a church for the Byzantine Empire. It was the third church built in the same spot. The building finished in the year 537. It had a dome that was one of the first of its kind. For a time, it was the biggest inside space in the world. Many people see it as a great example of Byzantine architecture. Its design, new at the time, affected how buildings were built later.

From the year 360 until 1453, the building was mostly an Eastern Orthodox church. For a short time, from 1204 to 1261, it was a Roman Catholic church because of the Fourth Crusade. After the Ottoman Empire took over Constantinople in 1453, it was changed into a mosque. It stayed a mosque until 1935. Then, Turkey made it a museum as part of the country’s rules. In 2020, Turkey changed it back to a mosque that is used for prayer. This change caused talk around the world.

Emperor Justinian I from the Byzantine Empire ordered the building we see now. It was built between 532 and 537. It was the main Christian church in Constantinople. Two Greek thinkers, Isidore of Miletus and Anthemius of Tralles, planned the building. Its full name was the Church of God’s Holy Wisdom. This was the third church with that name in this place. The church before it was destroyed during a time of trouble called the Nika Riots. Hagia Sophia was the seat of the main bishop of Constantinople. It was the biggest church in the world for nearly a thousand years, until a church in Seville, Spain, was finished in 1520.

The Hagia Sophia set a standard for Orthodox church buildings. It influenced many other buildings. Some examples include the Hagia Sophia in Thessaloniki, a church called Panagia Ekatontapiliani, and several mosques built by the Ottomans like the Şehzade Mosque and the Süleymaniye Mosque. For almost a thousand years, it was a very important place for Eastern Orthodox Christianity. It was given to Holy Wisdom. People saw it as a special building of the Byzantine and Orthodox world. A big event happened there in 1054: the main bishop, Michael I Cerularius, was formally separated from the Roman Catholic Church. This event is seen as the start of the split between the Eastern and Western churches. In 1204, during the Fourth Crusade, it became a Roman Catholic church under a group called the Latin Empire. But in 1261, when the Byzantines took back control, it became an Orthodox church again. A famous person, Enrico Dandolo, who was the leader of Venice and helped plan the Fourth Crusade and the attack on Constantinople, was buried inside its walls.

After the Ottomans took Constantinople in 1453, Sultan Mehmed II ordered it to become a mosque. It was the main mosque in Istanbul until the Sultan Ahmed Mosque was finished in 1616. Becoming a mosque meant many changes. Things like bells, the altar, and baptism areas were taken out. Pictures of Jesus, Mary, and Christian saints were either removed or covered up. New parts for Islamic prayer were added, like a mihrab (a place showing the direction of Mecca) and a minbar (a pulpit). Four tall towers called minarets were also added. At the same time, the main bishop moved to another church.

Hagia Sophia was used as a mosque until 1931, when it closed for repairs. In 1935, it opened again as a museum. This was part of Turkey’s plan to be a country separate from religion. It became a very popular place for visitors. In July 2020, a court in Turkey said that the decision to make it a museum in 1934 was not right. The court said it should be a mosque based on the wishes of Sultan Mehmed II when he first changed it. People who supported this change said it was fixing its rightful status. However, groups like UNESCO and the World Council of Churches, along with leaders from other countries, did not agree with the change. Many Muslim leaders in Turkey and other countries supported it.

Hagia Sophia shows how Istanbul, which used to be the capital of three big empires, changed over time in culture and religion. It is a UNESCO World Heritage Site. This means it is one of the world’s most important old buildings. It has been rebuilt many times and shows the hopes of rulers and the changes in history. Emperor Justinian built the Church of Holy Wisdom. It was the biggest church in the world for a thousand years and showed great building skill.

After the Ottomans took control of Constantinople in 1453, Hagia Sophia was changed to be the city’s first main mosque. Sultan Mehmed II started big repairs. He made the building stronger and added Islamic parts like minarets, mihrabs, minbars, and decorative writing. Christian symbols were covered with plaster. Ottoman decorations changed how the inside looked. Over the years, more things were added, like a school, a place to give food to the poor, fountains, and a library.

More than just a mosque, Hagia Sophia shows a long history and is a wonderful example of building design that shows what people could do over many years. In 1934, Turkey made it a museum as part of its goals to be a secular country. But a big moment happened in 2020 when it was officially made a mosque again. This brought back talk about its meaning in Turkey today.

Around the middle of the 1400s, the old capital of the Byzantine Empire was under Ottoman rule. Hagia Sophia was changed for Islamic prayer. The first Friday prayers held there showed its new purpose. The building was not in the best shape from not being cared for and from fighting. But work was done to fix up its important inside areas. Instead of taking away its history, the Ottomans covered Christian things but kept the building strong.

During this time, Hagia Sophia got important updates. The four tall minarets, which people know it for now, were added. Repairs in the mid-1800s included large round signs with Arabic writing. New columns that looked like old Byzantine ones and marble decorations from the Ottoman time were also added. When it became a museum in 1935, it showed that Turkey was becoming a secular country. In 2020, after many years of people asking for it, it was changed back to a mosque. This shows its importance in Turkey’s changing identity.

Few buildings in history have changed as much as the Hagia Sophia. It shows the rise and fall of powerful groups, the mixing of Christianity and Islam, and how time passes. It is a special example of different building styles coming together. From when it was first built by the Byzantines to how the Ottomans changed it, it is a living witness to Istanbul’s rich history. Here, old ways come together in a beautiful way.

Architecture

The Hagia Sophia is a real good example of building from the Byzantine times. It is quite large inside. The walls have beautiful pictures made from small tiles, called mosaics. There are also tall marble pillars and other fancy decorations. This place really shows how talented people were at art and building back then. Emperor Justinian was the one who had it built. It was a super special building for its time. For almost a thousand years, it was the biggest church anywhere in the world. Then, a church in Spain called the Seville Cathedral got finished and was bigger.

They built it using bricks and a special mix called mortar. The layers of mix between the bricks were thick, thicker than the bricks themselves. The mix was made from sand and little pieces of broken pottery. This way of building was kind of like what the old Romans used, sort of an early type of cement. They also put pieces of iron, like clips and ties, inside the walls. This helped make the building stronger so it could stand for many, many years.

This big church by Justinian shows the best building ideas from the time right before the Byzantine era. But it also started new building styles that became known as Byzantine. The building was a very big deal. It influenced how churches were built and used in many different parts of the world, not just where the Byzantine Empire was. It even had an effect on how some big buildings were designed in lands where people followed the Islamic faith.

Structural Composition and Geometric Design

Inside the Hagia Sophia, it is really big and arranged in a not-so-simple way. The main part of the building has a very large dome right in the middle on top. This big dome goes up super high, like 55.6 meters (that’s about 182 feet 5 inches) from the floor. The big weight of the dome is held up nicely by a ring of 40 windows that have rounded tops.

Over a lot of time, people had to do repairs and fix things. Because of this, the dome is not perfectly round anymore. It got a little bit of an oval shape. Its width across is a little different when you measure it in different spots. It’s between 31.24 meters (102 feet 6 inches) and 30.86 meters (101 feet 3 inches).

On the side where you walk in (that’s the west side) and on the other side where they used to hold church services (the east side), there are big openings with rounded tops. These openings lead into spaces covered by half-domes. These half-domes are about the same width as the main big dome. And then next to these, there are even smaller half-domes. It makes the domes look like they step down in size.

All these different domed parts come together. They make a long and large open space inside. And right over this space is the great big central dome. This makes a really wide open area inside, measuring about 76.2 meters (which is 250 feet) from one end to the other.

Mathematical Precision in Construction

The geometric principles underpinning the construction of the Hagia Sophia are thought to have been influenced by the mathematical works of Heron of Alexandria, a groundbreaking Hellenistic mathematician from the 1st century AD. His methodologies offered effective solutions for the significant challenge of covering extensive areas with large-scale vaults. According to researchers Svenshon and Stiffel, Heron’s prescribed values influenced the architects, especially through a numerical system based on side-and-diagonal number progressions. This system, as seen in ancient Babylonian cuneiform texts, utilizes proportional relationships where a square’s side measures 12 units and its diagonal measures 17.

The central square of the Hagia Sophia features four sides, each extending roughly 31 meters, a dimension previously believed to correspond to 100 Byzantine feet. However, Svenshon subsequently suggested that the true measurement is 99 feet—an alteration that corresponds with the 70:99 ratio found in ancient mathematical sequences. This precise measurement yields a diagonal length of 140, a practical figure for carrying out the dome’s engineering with exact mathematical accuracy.

Floor

The Omphalion, a stunning marble section of the Hagia Sophia’s floor, holds deep historical importance as the coronation site of Byzantine emperors. The stone flooring of the structure, dating back to the 6th century, quietly reflects centuries of imperial magnificence. Following the initial collapse of the vaulted ceiling, fragments of the broken dome lay strewn across the original Justinianic floor. In 558, the dome was reconstructed, with a new layer added over the existing debris. From this moment onward, the flooring transformed into a vital element of the church’s sacred rites, with various colored marbles and stones marking significant locations within the liturgical space.

The floor, primarily made of Proconnesian marble from Marmara Island in the Sea of Marmara, showcases the grandeur of Constantinople’s architectural heritage. Additionally, Thessalian verd antique marble, sourced from Roman Greece, adorns the structure, its rich green veins flowing through the nave like meandering rivers.

Writers and poets have often celebrated the floor’s enchanting beauty, frequently comparing it to an expansive sea. Paul the Silentiary, a Byzantine poet from the time of Justinian, imagined the ambo and its connecting pathway to the sanctuary as an island floating in a vast ocean. An account from the 9th century likened the floor to rolling waters, a perspective mirrored by Michael the Deacon in the 12th century. During the Ottoman conquest of Constantinople, Sultan Mehmed II reportedly ascended the galleries to admire its magnificence—chronicler Tursun Beg depicted it as a tumultuous, frozen sea. Ottoman authors lauded its aesthetic beauty, with Tâcîzâde Cafer Çelebi poetically likening the marble waves to the gentle undulations of a real ocean. On July 22, 2020, this historic floor was covered by a carpet.

Narthex and Portals

The Imperial Gate is a large entrance between the inner and outer front rooms. Long ago, only the Byzantine emperor used this gate. A long path starts in the northern part of the outer front room. It goes up to the upper floor, giving a view of the big inside area.

Upper Gallery

The upper floor is shaped like a horseshoe. People also call it the matroneum. It goes around the main part of the building on three sides. The only break is at the rounded end part called the apse. This space was usually for the Empress and the women who were with her. This floor has many different mosaics. The most beautiful ones are in the southern part.

In the northern part of the upper floor, there is something special from long ago: carvings called runic inscriptions. People think the Varangian Guard made them.

The outside walls of Hagia Sophia show damage from earthquakes and other natural events. Because of this, people did detailed studies using ground-penetrating radar (GPR). These studies found weak spots inside the upper floor. They also showed that the dome’s shape was a little different from how it was first built.

Dome

Many people like the dome of Hagia Sophia, including history experts, builders, and engineers. They like how it was built in a new way. Four triangle-like shapes called pendentives hold up the dome. This was a new way to build back then. These shapes help move the dome’s heavy weight down. This stops the sides from pushing out too much. This big dome was the largest pendentive dome in the world until St. Peter’s Basilica was finished.

The dome is 32.6 meters (107 feet) across. It is only 0.61 meters (2 feet) thick. It is made of brick and wet cement mix. The builders used light materials, like brick and mortar, instead of heavy stone. This was important for building the dome. These materials were easier to shape and use for such a big structure. Rowland Mainstone, who studies old buildings, said the dome walls were probably not thicker than one brick.

But the dome was still very heavy, and this caused problems. The first dome completely fell apart after an earthquake in the year 558. Isidore the Younger built the dome again in 563. The new dome had 40 strong ribs and was built 6.1 meters (20 feet) higher. This helped lower the sideways pressure. Even so, parts of this new dome also fell down. In 2021, only the north and south parts of the dome from the 562 building were still there. These parts have 14 ribs in total.

Problems happened also because of mistakes made when building. The builders used too much wet cement mix compared to the bricks. This made the walls weak. The wet cement mix was not dry when more parts were put on. So, the walls started to lean out when the dome’s heavy weight was put on them. Isidore the Younger had to make these walls stronger and fix them before he built the dome again. He used a structure with ribs, like an umbrella, to help send the weight better through the pendentives down to the ground.

Light inside the building makes the dome look like it is floating. This light comes in through windows around the bottom. Forty windows around the bottom make this happen. The windows also make the dome less heavy and let light fill the inside.

Buttresses

Over hundreds of years, workers added more buttresses to help the building stay strong. People often say the western flying buttresses came during the time of the Crusaders. But these buttresses first started in the Byzantine period. This shows how skilled Roman builders were with this method. You can see examples in the Rotunda of Galerius in Thessaloniki and the San Vitale church in Ravenna. Later, when the Ottomans were in charge, the building needed more support. The famous builder Mimar Sinan watched over the building of 24 buttresses.

Minarets

The minarets show how the Hagia Sophia changed from a church to a mosque. These towers were added later by the Ottomans and were not part of the first Byzantine building. The first minaret was made of wood. It stood on a half-dome during the time of Sultan Mehmed II. This minaret was for calling people to prayer and making public announcements. That wooden minaret is not there anymore. Also, the oldest minaret we can still see is made of red brick. It was built around the time of either Mehmed II or the next leader, Bayezid II. The last three minarets are made of white stone. One is a thin one on the northeast side, built for Bayezid II. The other two are large ones on the west side. Sultan Selim II asked for these two to be built, and the well-known Ottoman builder Mimar Sinan made them. These tall towers go up about 60 meters (200 feet). They look good with the main part of the Hagia Sophia building. Over many years, people added detailed designs to the minarets. The designs from different times show the art styles of those periods.

Significant Elements and Ornamentation

Under Emperor Justinian, the inside of the Hagia Sophia had complex, swirly designs on the marble walls and floors. Shiny mosaics covered the large arched ceilings. In the curved spaces of the bema (a raised area), pictures of the archangels Gabriel and Michael are still easy to see in these mosaics.

Even though most of the art was not pictures of people or things, some pictures were there early on. A writer named Paul the Silentiary wrote about this in the late 500s in a book called Description of Hagia Sophia. In the curved spaces of the upper level, or gallery, there are designs made from small, carefully cut pieces of white marble. These pieces make soft pictures of plants and animals, set against black marble.

Later, more mosaics with pictures of people were added. But these were taken down during a time when people did not want pictures in churches, between 726 and 843. The mosaics you see now were put up after this time.

After the 800s, many pictures of people appeared. A big picture of Christ was put in the main dome. Pictures of saints, prophets, and church leaders were placed in the walls below the dome. Important people linked to the building, like Patriarch Ignatius, were also shown.

The galleries had pictures from the Gospels. Emperor Basil II had large pictures of angels with six wings painted on the four curved parts that hold up the dome. Later, the Ottomans put gold stars over their faces. But in 2009, one angel’s face was uncovered to look like it did before.

The Loggia of the Empress

In the middle of the Hagia Sophia’s upper level, above the main door and across from the apse (the rounded end of the church), sits the Loggia of the Empress. From here, the empress and the people with her could get a good view of the church services happening below. A round green marble stone marks the exact spot where the empress’s chair sat. This green marble is special, called verd antique.

Lustration Urns

Two large washing pots, made from single blocks of marble, were brought from Pergamon because Sultan Murad III wanted them. These pots were very old, from a time called the Hellenistic period. People used them in special washing ceremonies.

The Marble Door

This door is in the southern part of the upper level. Only members of church meetings could use it. It has pretty pictures of fruits and fish. People said these pictures had a deep meaning. One side was said to stand for heaven, and the other, hell. The door led into a room where church leaders had important talks and made decisions about church matters.

The Nice Door

The Nice Door is thought to be the oldest part of the Hagia Sophia building. It comes from the 200s BC. The detailed designs on the door, showing shapes and plants, may have come from a temple that was not Christian in Tarsus, a place now called Mersin Province in Turkey. Emperor Theophilos put this door in the building in 838. Now, it is at the southern exit of the inside entrance area.

The Imperial Gate

The Imperial Gate is the biggest and most noticeable entrance to the Hagia Sophia. Only the Byzantine Emperor and the people right with him used this door. It is about seven meters tall. Old Byzantine writings say the wood for this door came from Noah’s Ark. This large door, made in the 500s, was damaged in April 2022. People all over the world said this was wrong. The Greek Foreign Ministry said the damage was bad. Turkish authorities started looking into it after people said someone took a piece of the door.

The Wishing Column

In the northwest part of the building is a curious column. People call it the Perspiring Column, Sweating Column, or Crying Column. It has a hole in the middle with bronze around it. A story says the column is always wet because of Saint Gregory Thaumaturgus in the year 1200. Some people believe touching the moisture on the column can help heal them.

The Viking Inscription

Writing made by a Viking soldier in the 800s has been found in the southern area of the Hagia Sophia. The writing, which uses Viking letters called runes, clearly says: Halvdan was here. This gives an interesting look into the Viking fighters who worked for the Eastern Roman Empire.

Mosaics of the Hagia Sophia

Early Christian Mosaics and Byzantine Iconoclasm

The first mosaics in Hagia Sophia came from the time of Emperor Justin II. They showed simple patterns, not pictures of people, which was common then.

But the most special mosaics were made much later, in the 900s and 1100s. This was after a time called Byzantine Iconoclasm. During that time, many religious pictures were destroyed.

In the year 1204, Crusaders from the West attacked Constantinople. They took many valuable things from the city, including golden mosaics from Hagia Sophia. Many of these treasures were taken to Venice. Doge Enrico Dandolo of Venice helped plan the attack with Prince Alexios Angelos. Alexios was the son of the emperor who had lost his throne.

Ottoman Transformation and 19th-Century Restoration

After the Ottomans took the city in 1453, Hagia Sophia became a mosque. The mosaics were slowly covered with plaster. This was because the Islamic faith usually does not show pictures of people.

Even so, some old writings from the 1600s say that some Christian pictures could still be seen.

From 1847 to 1849, two brothers, Gaspare and Giuseppe Fossati, who were builders from Switzerland and Italy, led a repair project. Sultan Abdulmejid I allowed them to make drawings of the mosaics. The Fossati brothers carefully drew the pictures. But they did not fix the mosaics. Instead, they painted over them.

They found pictures of six-winged angels, called hexapteryga, high up on the curved parts of the dome on the east side. After they drew them, they covered them up again.

The drawings and notes the Fossati brothers made are very important records. They keep information about many mosaics that were hurt or lost completely in a big earthquake in Istanbul in 1894.

One important mosaic in the Fossati records is the picture of Christ Pantocrator. He is shown inside a circle. This picture was likely high up on the main dome. This picture was later covered by Islamic writing. The writing says that God is the light of the universe.

Today, these important drawings are kept in a place called the Archive of the Canton of Ticino.

Notable Mosaics of the Hagia Sophia

Imperial Gate Mosaic

This picture is over the door called the Imperial Gate. In the past, only the emperor used this door. The mosaic is from a long time ago, maybe the late 800s or early 900s. It shows an emperor, probably Leo VI or Constantine VII, kneeling down in front of Christ. Christ is sitting on a throne. He is giving a blessing and holding an open book. Words from the Bible (John 20:19 and John 8:12) are written in the book. On each side of Christ, there are round pictures showing the angel Gabriel and the Virgin Mary.

Southwestern Entrance Mosaic

This mosaic is from when Basil II was emperor. People found it again in 1849 when some work was done on the building. The picture shows the Virgin Mary sitting with the baby Christ. Emperor Constantine stands next to them and holds a model of the city. Emperor Justinian I is also there, holding a model of the Hagia Sophia itself. Above the Virgin Mary’s head, there are letters in Greek that stand for “Mother of God.”

Apse Mosaic

The picture in the half-round part of the ceiling, called the apse, is a very famous example of old art from the Byzantine time. It shows the Virgin Mary sitting on a throne decorated with jewels. She is holding the baby Christ. The baby’s clothes are made of small gold pieces, which makes them look like they shine with light from heaven. Travelers who visited long ago, like Guillaume-Joseph Grelot in 1672 and Cornelius Loos in 1710, wrote about seeing this mosaic before the Ottoman leaders covered it up. The mosaic was found again between 1847 and 1848. Then, in the 1930s, a man named Thomas Whittemore uncovered it once more.

People who study history and art talk about when this mosaic was made. Some think it was made after people stopped breaking religious pictures in the Byzantine Empire, maybe when Photius I was the top religious leader (from 858 to 886). Others think it was made later, suggesting that an older picture of the Virgin standing up might have been replaced after earthquakes in the 1300s. Newer studies of a picture panel from a monastery show that the picture looks a lot like the apse mosaic as it is today. This means it was likely there by at least the 1000s or 1100s.

Later Byzantine and Post-Byzantine Mosaics

Emperor Alexander Mosaic

This mosaic is in a part of the second floor that is not very bright. It shows Emperor Alexander wearing his special clothes. He is holding a rolled-up paper (a scroll) and a ball with a cross on top (an orb). People thought this mosaic was lost in an earthquake in 1894. But in 1958, it was found again. It was not under plaster, but under layers of paint.

Empress Zoe Mosaic

This mosaic is from the 1000s. It shows Christ in the middle. On the sides are Emperor Constantine IX and Empress Zoe. They are holding things to give as gifts. Over time, the picture was changed. This shows that Zoe’s earlier husbands were in the mosaic before, and their faces were changed to show the faces of the people ruling at that time.

Comnenus Mosaic

This mosaic was made in 1122. It shows the Virgin Mary holding the baby Christ. Emperor John II Comnenus and Empress Irene, his wife from Hungary, are giving gifts. Their oldest son, Alexius, is pictured on a nearby pillar. The picture of Empress Irene is very clear. It shows her braided blonde hair, pink cheeks, and gray eyes, which show she was from Hungary.

Deësis Mosaic

The Deësis mosaic was made in 1261. Many people think it is the most beautiful mosaic in the Hagia Sophia from the Byzantine time. It was made after the city was taken back from the Latin rulers, which was a return to the Eastern Orthodox Christian faith. The mosaic shows Christ. Next to him are the Virgin Mary and John the Baptist, looking serious and asking for God’s kindness for all people. The way it is made shows a high level of skill, like the art being made in Europe at that time.

Northern Tympanum Mosaics

These mosaics are high up on the walls and were saved because of where they are located. They show important religious figures like Saints John Chrysostom and Ignatius of Constantinople. They wear white clothes with crosses and hold decorated Bible books. Many other mosaics on these high walls were ruined because of the frequent earthquakes.

20th-Century Restoration and Conservation Efforts

In the 1930s, a group called the Byzantine Institute of America worked on the Hagia Sophia. Thomas Whittemore led this work. They uncovered many mosaic pictures that had been covered up with plaster. They found many important artworks. However, some simple crosses stayed hidden.

Fixing the building is still a complex job. People try to find a way to show both the Christian pictures and the Islamic art respectfully. A big discussion point is whether to remove the Arabic writing in the main dome. People want to know if the old picture of Jesus, called the Pantocrator, is still underneath and if it should be shown. This question causes a lot of disagreement.

The building’s structure has become weaker over time. This happens naturally. Rainwater also gets inside, and salt builds up from the water. This makes the damage worse. Experts who care for old buildings say it is important to guide extra water away. This stops more harm from happening.

Scientists recently used special tools to look under the ground beneath the Hagia Sophia. They studied the structures there. They found hidden spaces underground. These spaces might have greatly helped the building stay strong during earthquakes. The study showed the building’s base sits on a natural rock slope. This helps explain why it has stayed up through many earthquakes over hundreds of years.

The Hagia Sophia is a great example of beautiful art and building design. Its mosaics tell stories of changes, faith, and how it has lasted for a long time.

Architectural Legacy of the Hagia Sophia

The Hagia Sophia has been very important for hundreds of years. It has shaped how many churches and other religious buildings look all over the world.

The Church of Saint Sava in Belgrade is one building that looks like it. It copied the main design, with a big central dome over a square base.

Many buildings have used the special design of the Hagia Sophia. They have a large dome on top. Curved parts underneath help hold it up. There are also two smaller half-domes next to the main dome. These help the building stay strong. In buildings from the Byzantine time, you can see this in the Hagia Sophia in Thessaloniki and the Hagia Irene church. The Hagia Irene was changed a lot by Emperor Justinian. A dome like the one in Istanbul was added.

The Ottoman Empire was greatly inspired by the Hagia Sophia. They used its ideas about space when they built mosques. The Süleymaniye Mosque and the Bayezid II Mosque show this. Ottoman builders often made the idea even bigger by putting four half-domes around the main dome instead of two. The Sultan Ahmed Mosque, the Fatih Mosque, and the New Mosque in Istanbul also show this change. They have very large open areas with columns. This is like a nod to the Hagia Sophia, which used to have a courtyard, but it is gone now.

A building style called Neo-Byzantine also kept using the Hagia Sophia’s look. Buildings like the Kronstadt Naval Cathedral, Holy Trinity Cathedral in Sibiu, and the Poti Cathedral copied how the inside of the Hagia Sophia looks very closely. The Kronstadt Naval Cathedral is almost the same size and layout inside. The marble walls also look like the older Byzantine church.

Some buildings, like the Church of Saint Sava, use four half-domes like the Ottomans did instead of two. Others, such as the Catedral Metropolitana Ortodoxa in São Paulo and the Église du Saint-Esprit in Paris, changed the first plan. They put flatter half-domes in the curved wall areas under the main dome. That last building, the one in Paris, is amazing, but it is only two-thirds as big as the Hagia Sophia.

Some buildings mix the Hagia Sophia’s look with a design shaped like a cross. The Cathedral Basilica of Saint Louis in St. Louis has half-domes in its side arms. The tops of its columns and its mosaics look a lot like old Byzantine ones. Other important examples are the Alexander Nevsky Cathedral in Sofia, St. Sophia’s Cathedral in London, Saint Clement Catholic Church in Chicago, and the Basilica of the National Shrine of the Immaculate Conception.

The Hagia Sophia has also been important for how synagogues are built. Its effect goes beyond Christian and Islamic buildings. Buildings like the Congregation Emanu-El in San Francisco, the Great Synagogue of Florence, and the Hurva Synagogue all have parts that were inspired by the Hagia Sophia’s amazing inside spaces and how creative it is as a building.

The Hagia Sophia is a truly important building. Its story includes fixing old art and dealing with water damage. Its design has also helped shape many other important buildings around the world, showing its lasting power and beauty.