Skip to main content

Religion has always been a sensitive subject in human history and it is believed that places of worship were the first buildings in the world.

To move forward in the field of architecture innovations first we need to understand our past. Fortunately, many buildings around the world were witness to human history and can still tell the story.

One of these buildings is the Hagia Sophia in Istanbul, the former capital of Turkey. The story of Hagia Sophia spans over many centuries and it is linked to many innovations in the world of construction. Over the 1,500 years that have passed since its first opening, Hagia Sophia is well linked to the history of Istanbul, as well as to the history of the world.

Hagia Sophia was first built as a basilica for the Christian Church in the 6th century and it shortly became the symbol of both Orthodox Christianity and Byzantine architecture. Through the centuries, as the dominant culture shifted in Turkey, it became a landmark of the Muslim world as the Ottomans conquered Constantinople ( the name of Istanbul before the ottoman occupation). Soon after its completion, the dome and the newly built Hagia Sophia became a symbol of Orthodox Christianity and an inspiration for later religious spaces of both Orthodox and Muslim world.

Hagia Sophia

A tumultuous construction history

Besides this, Hagia Sophia is also a symbol of craftsmanship and endurance. They say that three’s a charm, and that’s exactly what happened with the basilica – the third version of the Hagia Sophia was finally successful and it is still standing today.

The three Hagia Sophias

The first Hagia Sophia was built under Emperor Constantius in 360 CE. Because it had a wooden roof, it was burned to the ground in 404 CE during some riots in the city of Constantinople.

The second Hagia Sophia was completed in 415 CE under Emperor Theodosios II and this time it was a bigger structure, with 5 naves and a monumental structure. Unfortunately, this second one was also covered with a wooden roof, so it was just a matter of time until it burned again. The inevitable happened though, a century after its completion during another riot in the city. Because the structure was too damaged, Emperor Justinian I ordered its demolition in 532 CE and the building of a new and improved version of the Basilica.

For the third Hagia Sophia, Justinian I commissioned two greek architects – Isidoros of Miletus and Anthemios of Tralles – and it was completed in 537 A.D. The one that you can visit today in Istanbul is more or less the same basilica that Justinian walked in for the first religious service on December 27, 537 CE.  


The design of the basilica

The Emperor requested the two architects to build the greatest basilica in the whole Roman Empire and so they did. By combining mathematics with structures, the architects made use of a new architectural concept. For it to cover the largest interior space possible, they proposed an innovative construction method – a dome supported by pendentives. Hagia Sophia’s circular dome is supported by four triangular pendentives which transition the efforts of the dome to a square supporting structure. This way, any massive pillars or columns that might interrupt the interior space were remove.

The final shape of the basilica is almost a square – length 81 m and width 73 m, while the nowadays cupola hovers 55 m above the interior floor. The dome of the new structure was built using bricks and it was considered the largest in the world, until the construction of Duomo of Florence in the 15th century CE.

The remarkable structure needed a remarkable interior design as well. It is said that to create such a grand and monumental construction that would be the symbol of Christianity and of the Byzantine Empire, Emperor Justinian I decreed that all provinces will send architectural pieces for use in its construction.

The material used was marble for the floor and walls mosaics that came from Anatolia and Syria, bricks for the walls and the dome that were transported from Northern Africa. The interior 104 columns were imported from Greece, from the Temple of Artemis in Ephesus and from Egypt.

The transformation into a mosque

As a battle of religion and power between the empires, Hagia Sophia became a symbol of winning and conquering. After the conquering of Constantinople in 1453 by the Ottomans led by Sultan Mehmed the Conqueror, the basilica entered a new era.

Shortly after, the Ottomans started the process of transforming the Christian Basilica into a mosque, as Islam was their central religion. Many of the original Christian-themed mosaics were covered with Islamic calligraphy and a mihrab was installed in the wall to indicate the direction toward Mecca, a tradition in all mosques. In the nave, eight massive medallions with Arabic calligraphy were hung on the columns.

Outside, there were built four minarets, for religious purposes (for the call to prayer) and structural reasons to fortify the structure. Between 1847 and 1849, the Hagia Sophia underwent an extensive renovation led by Swiss architects the Fossati brothers.

Hagia Sophia’s recent history

From 1935, after the Republic of Turkey was established, Hagia Sophia was opened as a museum. In July 2020, the Hagia Sophia was again declared a mosque by the Turkish Council of State and President Erdoğan.

architecture Hagia Sophia

The structural beauty of the interior design

The first dome, besides being an innovative concept, had its construction flaws, as Isidore the Younger, the nephew of Isidoros of Miletus, would discover. The first problem was that because the basilica was first constructed in a rush, the bricklayers applied more mortar than bricks and they didn’t wait for a layer of mortar to set before applying the next level of bricks. The resulted shallow arc of the dome couldn’t transmit well the forces and weight of the structure into the supporting piers, causing the already weakened walls to partly collapse in 557 A.D.

Isidore the Younger, the one that reconstructed Hagia Sophia, proposed a higher dome, with a bigger and rounder arc. For the forces to transmit correctly, he also added 40 ribs to the dome to provide support. Additionally, most of the original walls and semi-domes had to be also reconstructed to better hold the new dome.

By now it would be obvious why the 20th Century architects and engineers were so fascinated by the scale of Hagia Sophia and how it was designed, executed, and built.

Hagia Sophia is a very important lesson about how the search for beauty can impact and innovate the construction world. Some of the main characteristics of the basilica, like its monumentality, its interior spaciousness, harmony and symmetry, couldn’t be possible without the structural innovation used for building the dome. Therefore, the pendants system used should be first seen as a choice made out of aesthetic reasons.

The innovative structure of the dome

The innovative structure of the dome with pendentives

The relationship between mathematics and structural mechanics that is portrait in Hagia Sophia’s dome is the main characteristic of Byzantine Architecture. The design easily becomes the symbol of this type of geometric architecture, where beauty comes from aesthetically pleasing forms and lines that were a result of the deep understanding of how structures work.

Another famous characteristic of the basilica is the intricate Byzantine mosaics that decorated the interior walls and the dome. They were made from gold, silver, glass, terra cotta and colourful stone and they portrayed Christian scenes and figures. The pendentives were covered mosaics of six-winged angels called hexapterygon.

The interior mosaics were covered with Islamic calligraphy after the Ottoman conquering and the transformation of Hagia Sophia in a mosque. They were discovered in the 20th century after it became a museum and people were allowed to explore the insights into how the basilica was built.

There is no doubt by now about the revolutionary structural system of the dome with pendants were used for the first time on a large scale, but there are more interesting aspects that make this building possible. Hagia Sophia is the best example for showing how durable a brick building can be. However, the special brick aggregate, which is “lighter and more plastic than solid stone or concrete” allowed the building to face considerable earthquakes in this area.

The legacy of Hagia Sophia

We can easily say that the monumentality and beauty of Hagia Sophia conquered everyone. It influenced how religious spaces would be built in two major religions: the Orthodox churches and the Islamic mosques. After the fall of Constantinople, the Sultan Mehmed the Conqueror didn’t hesitate to transform the Christian basilica into a mosque, preserving and transmitting the Byzantine heritage into a new form and era.

Many places of worship from both religions were influenced by it. Let’s take for example the famous ottoman architect Sinan, that designed many Islamic mosques in the time of Suleyman the Magnificent inspired by Hagia Sophia and other byzantine structure. He used the same dome with pendants and parallel semi-domes and walls to create big interior spaces.

Besides Islamic mosques, Hagia Sophia influenced Greek and Russian Orthodox architecture. It is also believed that Russian Orthodox basilicas in Russia were an effect of the early contact with Constantinople in the 10th century.

Hagia Sophia is a stark example of what is the power of the well-thought architecture of the places of worship. Even in the time when it was technically just a museum, the vocation of the space and what it symbolized had a deep impact on the people. Without its interior religious symbols, we can dare say it is a perfect religious space that can integrate any religion because of the feeling that architecture and the interior scenery creates.

The history of architecture is the history of mankind and we should understand it and try to learn from it. Many remarkable buildings stand the test of time and the pages of their history books are still being written word by word.


Hagia Sophia

Hagia Sophia.

Hagia Sophia.