Hazmburk, Medieval castle ruins in Klapý, Czech Republic

Hasenburg is a Gothic castle ruin on the summit of the hill of the same name at 429 metres, above the village of Klapý. Two towers survive: a taller rectangular one and a lower rounded one, with palace walls and a cistern between them. The slopes below are protected as the Vrch Hazmburk natural monument.

The Gothic castle was probably built by the Lichtenburgs in the first half of the 14th century; a first secure mention dates from 1335, when John of Luxembourg sold it to Zbyněk Zajíc of Valdek for 2,300 groschen. Zbyněk renamed it Hasenburg after the hare in his coat of arms, and the Zajíc family held it until 1558. It was recorded as deserted in 1586.

The castle's name comes from Zbyněk Zajíc of Valdek, who acquired it in 1335 and renamed it Hasenburg after the hare (Czech zajíc, German Hase) in his coat of arms; the family then called itself Zajíc of Hazmburk from 1337. Older sources also record the forms Zaječí hrad, Zajícův hrad and Hanžburek.

The site is accessible via a marked hiking trail starting from Klapý village, offering views across the surrounding countryside. Wear sturdy footwear since the climb is steep and the paths are uneven in places.

From 1440 to 1448, precious liturgical vestments from the Strahov Monastery were kept safe inside the castle. The castle was considered impregnable, and its garrison repelled Hussite sieges in 1424 and 1429. The extent of the original Lichtenburg castle remains unclear and awaits archaeological research.