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Hagia Sophia, Istanbul

Hagia Sophia, a historic architectural marvel in Istanbul, was built by Emperor Justinian as a Christian church. Its unique design combines a centrally planned space with a basilica, featuring a massive dome supported by pendentives. The structure's mystical atmosphere, created by light, gold mosaics, and colorful marbles, symbolizes the unity of heaven and earth. After the Ottoman conquest, it was converted into a mosque and later became a museum. A conversation with Dr. Steven Zucker and Dr. Beth Harris. Created by Beth Harris and Steven Zucker.

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Video transcript

(lively piano music) Voiceover: There are a handful of buildings throughout history that have changed the way we see architecture. Voiceover: We're standing in one of them. We're in Hagia Sophia in Istanbul. What was once Constantinople. Voiceover: Before that was Byzantium. Voiceover: First it was a Greek city then part of the Roman empire, and then Constantine decided to found a city here. Voiceover: Which he called the New Rome and which came to be known as Constantinople. Voiceover: Or the City of Constantine. That happened right at the time that Constantine was recognizing Christianity. By the end of that century Christianity would be become the official religion of the Roman empire. Voiceover: The emperor had his palace close by and that was the reason that the most important church was built here. Now the church that we're standing in is not that original church. That burned down. Voiceover: And so did the next church. Voiceover: They were actually burned during riots and the most famous riot took place in the 6th century and it's called Nika Riot. Voiceover: Against the emperor of the time, Justinian and Justinian was the patron of this church. Voiceover: This church was a way of putting to work a lot of people in the city that might otherwise riot, but it was also a way for him to express his power across the empire. Voiceover: This was one of many churches that Justinian built. This building though is the centerpiece of that building program. Voiceover: It's unbelievable. We're standing in this mountain of a building and in fact, to use that kind of geologic term is I think appropriate. One author said that standing here where we are in the sanctuary was like standing at the bottom of an enormous canyon. Now when this was built in the 6th century it was absolutely unique in the world. Not only for its scale, not only for its ambition, but also for its design. Voiceover: Justinian hired two theoreticians, two scholars who were well-versed in geometry and mathematical theory and physics to think about how to vault this space. The two churches that were here before had wooden roofs. Voiceover: Those were basic basilica structures. A kind of architecture that the ancient Romans were very comfortable with. We see that kind of architecture throughout the Roman empire, and so it would have been very familiar to the Roman emperors Constantine and Justinian. Voiceover: Justinian asked his architects to do something different, and instead of building a traditional basilica he had them build something that unified a centrally planned space with a basilica space. A basilica has a longitudinal format and a centrally planned space is based more on a circle. Voiceover: Let's talk about the basic geometries here. We have a dome that is phenomenally high. If you think about how the Romans handled domes and they did build very large dome structures. Think about the pantheon in Rome but in that case you have a round dome sitting directly on a round barrel. This building is doing something much different. This dome is on a square and so how in the world do you put the base of a round dome onto a square building? Voiceover: From that square base emerges two half domes forming a rectangle of space that reminds us of a basilica. Voiceover: How they've done it. They've done it with something called the pendentive. if you look at the base of the dome you see that it comes down on a series of four arches and a space between the four arches and the base of the dome it's kind of a triangle but it's curved. This miraculous thing happens. We know that dome must weigh an enormous amount and yet it seems to come down on the slenderest of points. Voiceover: What the architects did was hide the enormous stone piers that are doing most of the work of supporting the weight and the thrust of that dome. Domes exert an enormous amount of pressure not only down but also out. Part of the work of supporting the dome is also being done by the half domes on either side and on the east end three smaller half domes below that. This is the first time we see the dome on pendentives on this monumental scale. Voiceover: It was dangerous. It was incredible ambitious but it didn't work perfectly at first. Voiceover: No, there was an earthquake. Part of the dome collapsed and when it was rebuilt it was redesigned. The dome that we see now is taller than the dome that was here originally. Voiceover: By making it steeper it allows some of the lateral force to be reduced so that the weight comes more vertically down. The enormous thrust really did destabilize the building, and if you look carefully you can actually see some columns and other structural elements have been pushed askew. Voiceover: Here we are talking about the engineering. Voiceover: This is an engineering marvel. Voiceover: When you're inside the space you don't think about that. You think about the complexity of the space, the mysteriousness of the space. The way that the walls dissolve into light, the mysticism of this space. Voiceover: That's what this was all about. In fact, an early chronicler said it seems as if the dome is suspended from heaven and part of the reason for that is and this is just so incredibly ambitious. The architects pierced the base of the dome with 40 windows so that lights streams in under the dome. You begin to lose the structural elements between the windows and it seems almost to be continuous light. Voiceover: Light in Byzantine thinking is connected with ideas of perfection and the divine. Voiceover: The windows create a rhythm that almost sets the dome in motion and then all of that is resting on walls that are clad with marble that have rich veins and patterns that are all in motion. The floor is made of huge paving stones that seem as if it's almost a pattern of waves. Voiceover: It lacks the solidity of Ancient Roman architecture. Here we have a new Christian architecture for a new Christian Roman empire. Voiceover: For me it is the perfect expression of the transformation of the physical into the spiritual. This is a building that was the spiritual heart of the empire. Voiceover: The emperor in the east in the Byzantine empire which really was a continuation of he Roman empire but with vast amounts of territories that had been lost, that emperor was not just a political figure, he was also the head of the church. He appointed the patriarch, the man in charge of the church. This is very different than when we think about the pope in the western part of the empire. Voiceover: When important rites took place in this church and the emperor and the patriarch came together it was an expression of the unity of heaven and earth. Of political power and spiritual power. We were talking about the way that this building is an expression of mystery, and its structural qualities are beautifully hidden. One of the things that distracts our eye from the structure is the surface decoration. All of these upper surfaces that are not colored stone were covered with gold mosaic. Voiceover: Mosaic that had decorative patterns. Voiceover: Acanthus leaves, palm leaves. You could find crosses everywhere. What you couldn't find was mosaics that showed figures. This was a period in Byzantine history that was leading up to what we call the iconoclasm. Which was a point where there was a real crisis of images. When this church was built it was a clear decision to avoid any kind of figural imagery. Voiceover: The decision might have been because of concerns around the commandment against creating raven images. It also may have been to highlight the architecture instead of drawing your attention to Mary or Christ, but instead drawing your attention to overall mystical effect of the space itself. Voiceover: The color wasn't just from the mosaics. All these clear glass was originally colored. It was red, it was yellow, it was purple, it was blue, it was green and then you have the surface of the marbles. Justinian payed an enormous amount of money to import marbles from across his empire. He's brought the most beautiful, most elegant marbles that he could, and he's embedded them in the walls, what we call revetment and his workmen were able to saw these pieces of marble crosswise and then open them up like leaves of a book so that the patterns were actually mirrors creating this wonderful complex patterns. You have light streaming in the windows, gold mosaics, these colored marbles. All of which created this kaleidoscope of movement and energy. Voiceover: When the emperor stood with the patriarch of the orthodox church in this space they wore gold and purple and silver. Voiceover: There were gems embedded in the thrones. There was an enormous screen that protected the sanctuary and by some accounts it was 35 feet high completely covered in silver. Voiceover: You had the laity, normal people like us standing in the aisles and the galleries above, and then only the patriarch, the priest, the clergy and the emperor were allowed in this space that as you said was screened. You had a mystery within this mysterious space. What a spectacle. Voiceover: This building is almost 1500 years old so it's gone through a lot of changes. Voiceover: Change is visible all around us. The floors are worn and uneven. Parts of the marble revetment are lost and they've been painted instead. There's clearly mosaics that date from different periods of time. Most obviously there are Islamic inscriptions in the dome from when this building was made into a mosque. Voiceover: The Byzantine empire was ultimately conquered by the Ottoman [Turks] who were Muslims, and this city, Constantinople was the great treasure and the great gem in that city was this church. When this city was conquered one of the first things they did was transform it into a mosque. Voiceover: This functioned as a mosque until 1934 when it was secularized and made into a museum. Voiceover: What we've lost mostly though is all of the original Christian furnishings. Voiceover: Not just furnishings but relics, reliquaries. This was a space that was filled with holy objects. Voiceover: The reason for this is not when the Muslims invaded. The reason for this is when the Western European Christians invaded. Voiceover: Right and that happened in 1204. Voiceover: Instead of going to the Holy Land. Voiceover: To take back the Holy Land from the Muslims. Voiceover: The Crusaders owed the Venetians a lot of money which they couldn't pay and so they ended up sacking Constantinople instead. Voiceover: A lot of the great treasures that were once here are in Venice. They're scattered through museums all over the world. Voiceover: One can only imagine how rich this space must have looked when it was covered with gold and silver, when there were gems studding its most important furniture. Voiceover: When people were venerating the relics that were here and the icons that were here. Voiceover: When this was the center of the empire. (lively piano music)