Propylaea

The Propylaia is the classical Greek Doric building complex that functioned as the monumental ceremonial gateway to the Acropolis of Athens. Built between 437 and 432 BCE as a part of the Periklean Building Program, it was the last in a series of gatehouses built on the citadel. Its architect was Mnesikles, his only known building. It is evident from traces left on the extant building that the plan for the Propylaia evolved considerably during its construction, and that the project was ultimately abandoned in an unfinished state.