Canal of Xerxes

The Xerxes Canal was a navigable canal through the base of the Mount Athos peninsula in Chalkidiki, northern Greece, built in the 5th century BC. King Xerxes I of Persia ordered its construction, which was overseen by his engineer Artachaees, as part of Xerxes' preparations for his second invasion of Greece in the Greco-Persian Wars. It is one of the few monuments left by the Persian Empire in Europe.

Source: Wikipedia