The Regional Unit of Corinthia is known for its rich history and natural beauty. The Corinth Isthmus is the most famous canal in Greece, with about 15 000 vessels crossing it annually. The town of Loutraki is one of the best-known spa resorts in Greece, with continuous tourism development. The important ancient Greek city-state of Corinth was one of the wealthiest cities in antiquity, dominated by the Temple of Apollo, the legendary Glauke Fountain, the Lechaion Road, the Asklepieion, the ruins of the theatre and odeon, and the remains of fountains that adorned the city. The oldest castle in the Peloponnese is 3 km from ancient Corinth at Acrocorinthos, built on a 575 m hill, offering stunning views.