Odysseus Cave, Sea cave on southern coast of Mljet, Croatia

Odysseus Cave, also called Jama, is an oval sea cave on the southern coast of Mljet near Babino Polje, several dozen metres across. Its collapsed vault makes it look like a large hole in the ground from the land side, and the floor is filled with the sea. A tunnel about 20 m long, 4–5 m wide and only 1–1.5 m above the water leads in from the open sea; the water there is 8–10 m deep. Daylight never reaches the interior because of the high cliffs.

For centuries, sailors and fishermen along this part of the Adriatic used the cave as a natural shelter, taking advantage of the tunnel entrance to moor their boats inside. The connection to Homer's Odyssey came later and gave the cave a name that spread far beyond the island.

The name comes from Homer's Odyssey: local people hold that Mljet is the ancient Ogygia, where the nymph Calypso kept Odysseus for seven years. They point to the olives and vineyards growing right by the shipwreck site, as Homer describes. The legend is now more often attached to Malta than to Mljet.

Enter by swimming or in a small boat through the roughly 20-metre tunnel, whose sea entrance is 4 to 5 metres wide but only 1 to 1.5 metres above the water, with depths of 8 to 10 metres below. A very steep improvised staircase gives access from land. Daylight never reaches inside the Jama itself, so the colour spectrum appears on the water around noon in summer, not within the chamber.

No historical evidence links Mljet to Homer's Odyssey, and scholars treat the connection as a later invention rather than a documented fact. The name most likely spread through the stories of travellers who wanted to find a physical place tied to the ancient poem.