Mljet National Park makes up most of the island, and there are several villages, two salt water lakes - Veliko and Malo jezero, and a Benedictine monastery on the island of sv. Marija [St. Mary] . In Polače there are some of the best natural anchorages in the Adriatic.
Preserved from the Illyrian period, there are many fortifications and tombs, and the best preserved are those on the hill of Veliki Gradac, Veliko jezero and the fortress at Vodice, above the water source at Vodice at Babino Polje. The Roman Palace, which is the largest after Diocletian’s Palace in Split and the Arena in Pula, is a part of the valuable heritage of the island of Mljet.
Situated on the island of the same name, Mljet National Park is the most important protected area of the Dalmatian south. It is the oldest National Park at the Adriatic. The park covers the western part of the island, which many regard as the most alluring in the Adriatic, full of lush and varied Mediterranean vegetation. The park includes two deep bays which, due to their extremely narrow links with the sea, are regarded as and indeed named lakes: the Great Lake and the Small Lake. Mljet is also very rich in cultural heritage, the most prominent example being the complex of the 12th century Benedictine monastery. The monastery is located on a small island in the middle of the Great Lake and is set in a lush park. Over the course of centuries, numerous chronicles, dissertations and other literary works have been written here. Located within the monastery is the church of St Mary.