Olsztyn Founded in the 14th century by the Teutonic Knights, Olsztyn was reverted to Polish hands in 1466. The most important historic sight in town is the castle, housing nowadays a large museum, which can be enjoyed along with galleries and performances. The City Hall and St.Jacobs Cathedral are also well worth a look. Other monuments of architecture to visit: St. James' Cathedral, Old Town Hall on the Market Square - built in mid-14th century, the town walls and the Upper Gate (since mid 19th century known as the High Gate), the Jerusalem Chapel and the Church of St. Lawrence - built during the late 14th century.