Syracuse was founded by Corinthian settlers in 734 BC and was one of the most important colonies of Magna Grecia. The theater of Syracuse was built in the 5th century BC into the rocky sides of the Temenite hill. The altar of Hiero II was built in the 3rd century BC and is the biggest altar of Greek antiquity. Other important structures are the amphitheater and the Sanctuary of the Madonna della Lacrime. The archaeological site was declared a World Heritage site by UNESCO in 2005.