Since it was built in 537 AD, Hagia Sophia has been a Christian church, an Islamic mosque, and a secular museum. Built at the intersection of major fault lines, the structure has endured more than a dozen devastating earthquakes. How does it survive? An international team of experts investigates Hagia Sophia’s seismic secrets using radar, laser, and computer technologies—even building an 8-ton scale model to place on a motorized shake table to simulate the effects of an earthquake. Scientists race to discover how Hagia Sophia was built, why it still stands, and whether it will survive as Istanbul braces for the next major earthquake.