The famous round building at the Sanctuary of Athena Pronaia, Delphi, Greece, on a gloomy (but delightfully atmospheric) day (partially reconstructed, since the frequent earthquakes in the area have done a number on this and all the other ancient buildings in the area). Delphi was one of the more important religious sites of the ancient world (home of the temple of Apollo and his famous oracle), and is on the side of a rocky and very scenic mountain, making it particularly pleasant to visit.