Ostrý Kameň is a ruin of a castle located on a hill near the village of Buková, at an altitude of 576 meters above sea level. Fragments of residential and farm buildings, towers and walls from the Gothic period, as well as a Renaissance double cantilever have survived to this day. The whole thing is quite overgrown, but the hill overlooks the Little Carpathians and the Zagórska Lowlands. The red General Štefánik Trail also runs right next to the ruins. Well-marked hiking trails lead to the ruins.
The castle was built in the 13th century to defend the Czech Way. Initially, it was a royal property, then it was transferred to noble families. In the 18th century, the stronghold was damaged during the Rakoczi Uprising, and the Czech Road changed its course, which resulted in the decline of the importance of the castle. Soon it was abandoned, and the lack of care and exposure to destructive weather conditions and thefts caused the stronghold to quickly collapse.