Parthenon

While today assumed to be a piece of incredible architecture, the Parthenon had much religious and political significance in the days of its use. It was built for the goddess Athena but it wasn't necessarily used as our typical idea of a temple or church. The building instead housed the treasury of the Delian League, the key to Athens fiscal success and also the basis for many conflicts and military actions among its "protected allies."  The Parthenon is a huge columned structure, relying on the Doric style, and built to give the impression of perfect order and symmetry even though when closely observed, the architects have fudged measurements in order to trick the eye.  As a symbol, it is one of the foremost associated with Greece and one that the country ties closely to their tradition of democracy.