The Hymn to Delos by Callimachus is the longest of the six and the only one that does not refer to a god but to an island, the birthplace of Apollo.

The narrative has two main axes: one follows Leto's wanderings as she searches for a place to give birth, and the other follows Asteria's wanderings, which is an island with no fixed position in the sea but constantly moves around.

Leto had to face the wrath of Hera, who had assigned Ares to oversee the land and Iris to oversee the islands, so that no place would accept Leto to give birth.

Thus, three main episodes unfold: those of Thebes, the Peneus River, and the island of Cos. In the first, Apollo, still in his mother's womb, secretly prophesies the destruction of Niobe's children, who had mocked Leto for having only two children.

In the episode of the Peneus River, unlike other places, the river responds to Ares and accepts Leto, but she shows her magnanimity and refuses the river's offering because she does not want to suffer anything on account of her.

In the episode of Cos, Apollo himself, again secretly, prevents Leto from giving birth on the island because Ptolemy Philadelphus is destined to be born there. Here we see the second prophecy of the god, which concerns Philadelphus's actions.

Thus, the meeting of Leto and Asteria finally occurs, and Leto finds a place to give birth. Since then, Asteria ceased to wander, settled in a fixed place, was no longer "invisible" but visible (Delos), and changed her name.

In the last part, Callimachus refers to the honors that people pay to the island.