"Cape Sounion ... is the promontory at the southernmost tip of the Attic peninsula, 8 kilometres (5.0 mi) south of the town of Lavrio (ancient Thoricus), and 70 kilometres (43 mi) southeast of Athens. It is part of Lavreotiki municipality, East Attica, Greece." Source: Wikipedia.
"The original, Archaic-period temple of Poseidon on the site, which was built of tufa, was probably destroyed in 480 BC by Persian troops during Xerxes I's invasion of Greece. Although there is no direct evidence for Sounion, Xerxes certainly had the temple of Athena and everything else on the Acropolis of Athens, razed as punishment for the Athenians' defiance. After they defeated Xerxes in the naval Battle of Salamis, the Athenians placed an entire captured enemy trireme (warship with three banks of oars) at Sounion as a trophy dedicated to Poseidon." (Wikipedia)
"The temple of Poseidon at Sounion was constructed in 444–440 BC. This was during the ascendancy of the Athenian statesman Pericles, who also rebuilt the Parthenon in Athens. It was built on the ruins of a temple dating from the Archaic period."
"Archaeological evidence indicates that Sounion was a sacred area as far back as the Bronze Age," according to Ancient Greece. "... An inscription confirms that the temple was dedicated to Poseidon, and it was built upon the remains of an even earlier poros [a type of stone named after the Poros islands] temple whose foundations are still visible. This Archaic temple was razed by the Persians in 490 BCE [Wikipedia says it was 480 BC] when it still under construction. Very little is known about this earlier temple, but it is certain that it was a revered landmark, visible from afar as sailors approached or left the safety of the Attica harbors. The newer temple closely follows the size and plan of the more ancient one."
Video from 2016.