The Blue Mosque’s central dome, seen here, was modeled on Hagia Sophia’s. It measures 141 feet in height and 110 feet in diameter. While the dome itself is painted, the piers that support it, and the lower-level walls, are covered in tiles from Iznik (ancient Nicea), a city known since Byzantine times for its skill in ceramic painting. The predominantly blue color of these tiles is what gives the mosque its nickname.