The earliest evidence of dome architecture dates back to ancient Mesopotamia and the ziggurat of Ur-Nammu, built in the 21st century BC. Later, the Romans, such as the Pantheon, built domes in ancient Rome.
The Hagia Sophia, designed by the architects Isidore of Miletus and Anthemius of Tralles, was completed in 537 AD during the reign of Byzantine emperor Justinian I. Its dome is remarkable for its massive size and complex construction techniques. The diameter of the dome is approximately 31 meters (102 feet), and it rises to a height of about 56 meters (184 feet) from the floor of the basilica. The dome is supported by four massive piers and pendentives, triangular segments of masonry that transition between the square base of the dome and the circular base of the dome itself.
Before the construction of the Hagia Sophia, domes had been used in architecture for centuries, but the scale and complexity of its dome pushed the boundaries of engineering at the time. The dome of the Hagia Sophia is still standing today and remains one of the most iconic landmarks in the world.
