North of Smolenice is the village Buková with water reservoir and a marked route, which leads southward to the romantic ruins of the Castle Ostrý Kameň from the 13th century. The Castle was a royal border fort guarding the Czech road in the past. It is in decay since the 18th century though part of its walls, bastion, and adjacent buildings are still observable. The top of the Castle provides a nice view of the Malé Karpaty Mts. and the Záhorská nížina lowland.
References:Celje Castle was once the largest fortification on Slovenian territory. The first fortified building on the site (a Romanesque palace) was built in the first half of the 13th century by the Counts of Heunburg from Carinthia on the stony outcrop on the western side of the ridge where the castle stands. It had five sides, or four plus the southern side, which was a natural defence. The first written records of the castle date back to between 1125 and 1137; it was probably built by Count Gunter. In the western section of the castle, there was a building with several floors. Remains of the walls of this palatium have survived. In the eastern section, there was an enclosed courtyard with large water reservoirs. The eastern wall, which protects the castle from its most exposed side, was around three metres thicker than the rest of the curtain wall. The wall was topped with a parapet and protected walkway.