Cape Sounion is an easy day trip from Athens, and is the home of the remains (with reassembled columns, I'd imagine) of the ancient Temple of Poseidon perched on top of a bluff overlooking the sea. (It appears to be facing the double-peaked mountain in the distance on the left; it's accepted that the ancient Minoans, who were the pre-Greek inhabitants of the Aegean, often faced their temple/palaces toward double-peaked mountains, which echoed their "bull horn" religious symbols. Maybe the location and orientation of this much later temple were influenced by Minoan tradition? Especially since, with the decipherment of the Minoan/Mycenean Linear B writing, it's clear they [or at least their Mycenean not-long-after successors] worshipped Poseidon too... But that's just me speculating...)