The small village Klášter ("Monastery") lies about 10 km east of the small town Nová Bystřice not far from the Czech-Austrian border, 650 m a.s.l.

The village is named for the monastery founded here together with the church in 1491 near the spring of healing water. In 1533 the monastery (with the monks inside) was set on fire and destroyed by the Paulines. It was restored in 1626, but in 1785 it was closed by an edict of Emperor Joseph II. The buildings of the monastery were levelled in the 1950's and only the Church of the Most Holy Trinity with the so-called underground Red Passageway (from monastery to the church) have been preserved up till the present day.
The Church of the Most Holy Trinity is one of the most important Early-Baroque buildings in South Bohemia. It was built between 1668 - 1682 near the monastery. The single-aisled church with five side chapels and a tower has valuable Early-Baroque furnishings and stucco. The main altar was made by Viennese joiner K. Zeller in 1678.

The church and the part of the underground corridors are open to the public.