The island of Mljet lies parallel to the Peljesac peninsula. It is a green paradise, with thick forests of Aleppo pine, Karst caves, two picturesque salt-water lakes, many sandy and gravel beaches, and plentiful fishing grounds.

The western part of the island has been proclaimed a national park. Some ten villages are on the island, with beautiful beaches and places suitable for harpoon fishing. There are remains of Illyrian castles and also many ruins from the Roman times, including a well-preserved part of an early Byzantine palace, and an early Christian basilica in Polace.

The most valuable monument from the Romanesque period is the monastery on the small island in Veliko Jezero (Big Lake) - an island within an island! In the 12th century, the Benedictines built a monastery, around which a Renaissance building with strong walls and a tower was constructed in the 16th century.