Sparta is located in the region of Laconia, in the south-eastern Peloponnese. Ancient Sparta was built on the banks of the Eurotas River, the largest river of Laconia, which provided it with a source of fresh water. The valley of the Eurotas is a natural fortress, bounded to the west by Mt. Taygetus (2,407 m) and to the east by Mt. Parnon (1,935 m). To the north, Laconia is separated from Arcadia by hilly uplands reaching 1000 m in altitude. These natural defenses worked to Sparta's advantage and protected it from sacking and invasion. Though landlocked, Sparta had a vassal harbor, Gytheio, on the Laconian Gulf.