Winter sport resorts Wisła by the river of the same name and Korbielów, situated between the Babia Góra massif (1725 m) and Mt Pilsko (1557 m). In winter a network of ski lifts and ski trails operates on the slopes of Mt Pilsko. The river Olza running through Cieszyn, has been a division line between the Polish and Czech part of the town since 1920. The town centre situated on the Polish side has been well-preserved. Beautiful 18th and 19th century houses ring the large market square. On the Góra Zamkowa (Castle Hill), the Rotunda of St Nicolas calls for closer inspection. It is an exclusive example of Romanesque architecture appearing in Silesia in such a good shape.