The Temple of Apollo in Dorian style, second or third century BC. In its cella there was a perfectly preserved mosaic from the 2nd century BC, showing the symbols of Leto's children: Apollo's lyre, Artemis' bow and arrow. This is a copy, the original is in the Fethiye museum.
On Leto the WIkipedia has: In Greek mythology, Leto (Greek: Λητώ; Λατώ, Latō in Dorian Greek, etymology and meaning disputed) is a daughter of the Titans Coeus and Phoebe. Kos claimed her birthplace. In the Olympian scheme, Zeus is the father of her twins, Apollo and Artemis, the Letoides, which Leto conceived after her hidden beauty accidentally caught the eyes of Zeus.