The Temple of Poseidon is an ancient Greek temple located on Cape Sounion, about 70 kilometers southeast of Athens. It is dedicated to Poseidon, the god of the sea in Greek mythology. 

Built in the 5th century BC, the Temple of Poseidon is considered one of the major monuments of the Golden Age of Athens. It was constructed using white marble and features impressive Doric columns. 

The main purpose of the temple was to honor Poseidon and seek his favor for safe sea voyages. Sailors and merchants would often visit the temple to make offerings and pray for protection. The location of the temple, with its commanding view of the sea, made it a fitting place for such rituals. 

Today, the Temple of Poseidon is a popular tourist attraction, drawing visitors from around the world. Its picturesque setting and historical significance make it a must-visit destination for those interested in ancient Greek history and mythology.