Klapý Castle was probably built by the house of Lichtemburk, masters of many places in the neighbourhood since the end of the 12th century. The first preserved mention of the Castle comes from 1335, when it was acquired by John of Bohemia from Hynek of Lichtemburk, and soon sold to Zbynek Zajíc of Valdek. At that time the castle got its name from the coat of arms of Zbyněk Zajíc of Valdek. Kryštof of Házmburk sold his estates to John the Elder of Lobkowicz in 1558, owner of Zbiroh and Točník, but he did not settle at the castle. The Castle was later made a permanent part of the Libochovice estates. Even though the Castle was falling into disrepair for centuries, the solid structure of its two towers survived until the present. Remnants of the first gate can be seen today, which was located close to the central quarters.

The second bailey (lower castle) is protected by the so-called Black Tower, around which the fortifications turn, creating a very reliable place of resistance. The name of the tower is derived from its building material - dark basalt. The fortifications continued and made sort of a bailey around the inner quarters, the wall of which has also been partially preserved. There is a slightly larger courtyard to the west, with remnants of buildings and a cellar. A pathway leads from the Black Tower to the inner (upper) castle across higher ground, where remnants of houses were visible as late as in the 19th century. The robust White Tower with a partially preserved enveloping wall is accessible and offers a beautiful 360° view.

Many legends are connected to Házmburk, the main features of which are obviously hidden treasures. The typical skyline of the castle attracted a number of artists, among others Karel Hynek Mácha, Václav Beneš Třebízsky, Svatopluk Čech, Josef Kopta and Emil Filla. You can find a small snack kiosk on the premises.