Located at the western end of the Monleón village, next to a steep area that dominates the confluence of the Carnicero stream with the Alagón river, Monleón Castle was raised in the 13th century as part of the defensive walls that surround the village.
Its groundplan is an irregular trapeze, with the keep in the middle. The north and east wall of the enclosure are built later than the others, to obtain a fortified perimeter that defended the tower from inside the village. The square keep is made up of large granite blocks reinforced with ashlar masonry at its corners. The top is fitted with 8 turrets. In medieval times the keep could be accessed on the second floorlevel by means of a removable stair or drawbridge. Its interior was fitted with five floors.
In 1477 the castle was besieged by the troops of King Fernando the Catholic. The reason for this was that its lord; a Salamancan knight, Don Bernardo Maldonado the Tyrant, had been manufacturing false currency amongst other crimes that caused great damage to the surrounding territories.
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.