Sparta was a prominent city-state in Laconia, in ancient Greece. In antiquity, the city-state was known as Lacedaemon, while the name Sparta referred to its main settlement on the banks of the Eurotas River in Laconia, in south-eastern Peloponnese. Sparta was unique in ancient Greece for its social system and constitution, which were supposedly introduced by the semi-mythical legislator Lycurgus. His laws configured the Spartan society to maximize military proficiency at all costs, focusing all social institutions on military training and physical development. Leonidas I, “son of the lion”, was a king of the city-state of Sparta, and the 17th of the Agiad line, a dynasty which claimed descent from the mythological demigod Heracles and Cadmus. Leonidas had a notable participation in the Second Persian War, where he led the allied Greek forces to a last stand at the Battle of Thermopylae (480 BC) while attempting to defend the pass from the invading Persian army; he died at the battle and entered myth as the leader of the 300 Spartans. While the Greeks lost this battle, they were able to expel the Persian invaders in the following year.