The most important tourist sight in the only town of the county, Kuressaare (up to 1917 Arensburg) is the bishopric castle. Among the medieval castles in the Baltic countries this is the one that has survived best. The castle was built of chiselled dolomite blocks in the late 14th century. The basic plan of the building is a square with sides 43 metres. There are two towers on the northen side of the building: The Watch Tower, also called Tall Herman, and the Defence Tower or Sturvolt. The entrance to the castle is also situated on the northen side. In the centre of the building there is a quadrangular courtyard, surrounded by a vaulted gallery, so called cloister on the first and second floors.