Crkva Svetog Donata
Zadar's star attraction, this massive cylindrical structure is the most monumental early Byzantine church in Croatia. Initially called the Church of the Holy Trinity, it was probably inspired by plans outlined in a book by the Byzantine emperor Constantine VII Porphyrogenitus, De Administrando Imperio (On Ruling the Empire). Centuries later, it was rededicated to St. Donatus, the bishop here from 801 to 814. Legend has it that Donatus, an Irishman, was the one who had it built using stone from the adjacent Forum. The stark round interior features a circular center surrounded by an annular passageway; a sanctuary consisting of three apses attached to the lofty mantle of the church walls, set off from the center by two columns; and a gallery reached by a circular stairway. During the off-season (November to March), when the church is closed, someone at the Archaeological Museum next door may have a key to let you in.