Letoon or Letoum (Letoon, Λητῷον) in the Fethiye district of Muğla Province, Turkey, was a sanctuary of Leto located south of the ancient city of Xanthos, to which it was closely associated, and along the Xanthos River. It was one of the most important religious centres in the region though never a fully-occupied settlement. Letoon was added as a UNESCO World Heritage Site in 1988. Letoon was the religious centre of Xanthos and the Lycian League. Inscriptions found at the site indicate that it was where Lycian rulers declared their decisions to the public. It was continuously occupied from the 8th century BC to the end of the Roman period of occupation. The site was dedicated to the worship of the Letoids—the Greek goddess Leto, and her twin offspring, Artemis and Apollo. According to a myth, Leto was drinking at a lake in Lycia whilst fleeing with her children Apollo and Artemis from the anger of the goddess Hera. When local peasants tried to drive her away, she rebuked them and transformed them into frogs. Leto may have been identified with an early Luwian goddess whose cult was located with Letoon. The Letoids were designated as the Lycians' national gods. The sanctity of the site is the purport of an anecdote related by the 2nd century Greek historian Appian concerning Mithridates VI of Pontus, who was planning to cut down the trees in the sacred grove for his own purposes during his siege of Patara, but was warned against this sacrilege in a nightmare. The site remained active through the Roman period. It was Christianised by the construction of an basilical church. Archaeological finds at Letoon date to at least the 6th century BCE, and pre-date the Greek cultural hegemony in Lycia. The sanctuary was connected to Xanthos by a road that led up from Patara to the south. The foundations of the three Hellenistic temples dedicated to Leto and her children have been excavated since 1962, under the successive direction of the French archaeologists Henri Metzger, Jacques Des Courtils and Emmanuel Laroche.