Mljet national park (since 1960) is situated in the north-western part of the island; area 54 sq km. It comprises Small and Big Lakes and Soline. They are connected by narrow and shallow canals. Various plant communities are amply represented in the National Park: Aleppo pine (Pinus halepensis), holm oak (Quercus ilex) and thick underbrush.

Big and Small Lakes and Soline are very interesting phenomena; Small Lake is exposed to the natural process of eutrophication, so that there is no oxygen in lower layers. Mongooses are normally found in the forests; the southern coast of the National Park is the natural habitat of the sea bear (ursine seal).

In the southern bay of Big Lake is an islet on which the Benedictines built a monastery with the church of St. Mary in the 12th century. The church of St. Mary has Romanesque features. The vestibule with high reliefs (saints' representations) was probably built at the turn between the 12th and the 13th century. The defence tower with a quadrangular ground-plan dates back to the same period. On the north-eastern side of the church is a Romanesque bell tower. During the Baroque period, two side chapels with altars were attached to the church. In the 16th century, the old monastery building with a cloister and a large cellar on the pier side were integrated in a Renaissance two-storey building with a 30-m long front terrace. At that time the monastery complex was fortified (defence walls and towers in the southern corner). In 1869 the monastery was secularized and abandoned; until 1941 it housed the forest management of the island of Mljet; in 1959-1960 it was converted into a hotel.In recent times the church has been reintroduced as a sacral structure. The function of the monastery is still an open issue. The patron saint's day is the Assumption (15th of August).

The island of Mljet, with its National Park - a natural phenomenon set aside and protected by the highest form of nature conservation due to its landscape, vegetation, geological, cultural and historical values - ranks among the most attractive island landscapes.

It is famous for its wildlife - fallow deer, wild boars and especially for mongooses, which were brought in 1910 to exterminate venomous snakes - it seems that the island has always lived in legends, such as the one about a visit of Paul the Apostle or Emperor August.

Today, accommodation facilities (boarding houses, apartments), home-made food and local specialities (fish, spiny lobsters, cheese, wine), a network of visitor trails, traditional folk music and picturesque traditional costumes - all this will make a visit to Mljet as if "a dream came true". The harbours of Polace and Pomena are traditional destinations of boaters.