The Temple of Leto, a goddess who was in love with Zeus and triggered his wife, Hera, to be so angry Leto fled to Delos when she was pregnant. There she gave birth to no less progeny than Apollo and Artemis. Their temples stand next to the temple of Leto, who was the most important here.

The temples were, according to an inscription, built by King Arbinas in the end of the 5th century. The Leto temple was used as an annex to a much later church, which was built using stones from the other two, of which much less remains. The middel one if that of Artemis, the Apollo one to the east is somewhat better preserved.

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.