The islet of of St. Mary is located in the southern part of the Big Lake of Mljet. Its size is almost negligible - 120 m x 200 m. Remains of a Roman building were found on it, but it is by far the most famous for the Benedictine monastery of St. Mary from the 12th century. It was built in the period from 1177 to 1198. The Benedictines first built a monastery on the islet and then a church. The church has changed its appearance over the centuries under the onslaught of styles, Renaissance and Baroque.