ROTUNDA / ΡΟΤΟΝΤΑ
Built early C4 AD, probably as a temple for pagan worship or as a mausoleum for Constantine the Great. Nearly 30m high and with walls 6.3m thick, commissioned by emperor Galerius. Soon converted to Christian worship during the Byzantine era, then to a mosque during the Ottoman era. After the 1912 liberation it was dedicated to St George, although the minaret was retained [source: local signage]. Thessaloniki, Greece.
