The town castle dates from the 14th century. Only the main tower has been preserved up till this day. It has been called Kotnov since the 16th century.
The castle stood on the rock spit above the Lužnice river. It was built for the protection of the trade route leading along the river to the town Sezimovo Ústí. The Bechyňská Brána (Bechyně Gate), which was a part of the town walls, stood beside the tower.
The observation tower with nice views of the town is open to the public. A part of the Hussite Museum is located there as well.