Megalopolis is known for its ancient ruins situated northwest of the town centre, on both banks of the river Elisson. The ruins include an ancient theatre that used to hold up to 20,000 people and was 30 m (98 ft) tall. Other landmarks include the Thersileon with 67 pillars and a temple (11.5 m × 5 m or 38 ft × 16 ft). Herodotus reported the ancient belief that the Megalopolis area was a battleground of the Titanomachy.