Imperial Splendor

Hagia Sophia (537 CE) was the largest cathedral in the world for nearly a thousand years. Its dome — 105 feet in diameter — appears to float on a ring of windows that floods the interior with light. The historian Procopius wrote that it seemed "not to rest upon solid masonry, but to be suspended from heaven by a golden chain."

Justinian's architects developed and perfected the pendentive dome — a structural technique that places a circular dome over a square base using curved triangular sections. Though Roman builders had experimented with the idea earlier, Hagia Sophia's pendentives were the first on such a monumental scale, an engineering breakthrough that let its massive dome appear to float weightlessly.