Place me on Sunium’s marbled steep,
Where nothing, save the waves and I,
May hear our mutual murmurs sweep;
There, swan-like, let me sing and die.
Lord Byron: The Isles of Greece
The Temple of Poseidon was built in 440 BC, when Athens was led by Pericles. The first temple on the site, dating from the Archaic period, was destroyed by the army of Xerxes during the Persian invasion of Greece in 480 BC. If you need help to imagine what the temple might have looked like, the Temple of Hephaestus on the agora of Athens was built at about the same time, possibly by the same architect, and is in a much better shape.
Cape Sounion is a promontory on the southern tip of the Attica Peninsula, not far from Athens. You can reach it by coach from Athens taking either the coastal route or an inland route passing by the ancient mines of Laurium (whose silver enabled Athens to build its famous fleet). According to legend, Cape Sounion is the spot where King Aegeus threw himself off the rocks, giving his name to the sea in which he died. Cape Sounion is also famous as the location from which to watch the sun set over the Aegean Sea. There is a path leading down from the temple to the bay below and you can finish your visit with a swim in the crystal clear water. (Shame about the ugly hotel.)