Monemvasia is one of the most important medieval fortress-cities of Greece. It is also one of the most beautiful castles in the world. Its area consists mostly of a large plateau some 100 metres above sea level, up to 300 m wide and 1 km long, the site of a powerful medieval fortress. The town walls and many Byzantine churches remain from the medieval period. Monemvasia is built in a rock which is a connected with a narrow and unique road to the mainland. Thus, it had always been well protected from the raids of the barbarians. "Monemvasia" means "one-way".