From the former Gothic castle Kotnov only the rotund tower remained. Its other parts were gradually destroyed by new reconstructions in the 17th century. In the Hussite times the castle became an integral part of town fortifications. The tower is the oldest example of a battery tower in our territory - a beam with trolley was pushed out of the oriel window and used for pulling cannons up. Today it serves as an observatory tower. The neighbouring Bechyňská Gate houses museum expositions focusing on life and work in medieval society.