Bonilla de la Sierra castle has three wall sections and three turrets of different styles and origins. The main par of the castle was formed by the Tower of Homage, of the 14th century, it has matacanes and round arches, and under the tower is the main yard and the rooms. The castle contains 14th-century paintings.
It was the resting place of the prelates of the Ávila bishopric, and held important episcopal synods, as the one in 1384. Bishop Sancho Dávila had a wall built around the village in the 14th century.
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.