Hagia Sophia

Originally constructed as a Christian cathedral in 537 CE under Emperor Justinian I, the Hagia Sophia served for nearly a thousand years as the largest domed building in the world. Its massive central dome, measuring over 31 meters in diameter, appears to float above the nave through a ring of windows that flood the interior with diffused light. The building's successive roles as Byzantine cathedral, Ottoman mosque, secular museum, and active mosque again have left overlapping layers of mosaic, calligraphy, and architectural modification that make it a uniquely complex monument.