The Ostrovo-Ozersky Trinity Monastery is located on an island in the lake, 18 versts from the district town of Gorbatov, near the village of Vorsma. Its foundation is linked to the activities of the hermit Macarius in the second half of the 16th century, with the support of Prince Boris Cherkassky. Macarius was buried in this monastery. In 1662, the monastery was restored by Prince Yakov Cherkassky. The Kazan Icon of the Mother of God, gifted by Prince Boris Cherkassky, is kept here, and processions are held with it through the villages of the diocese.

Today, restoration work is underway for the Kazan Church, which was destroyed in the 1930s during the Soviet era. The church was built in 1691-1692 by architect P. Potehin. Nearby were the refectory, kitchen, cellar, icehouse, and part of the brotherhood's cells.