The castle of Olost is located in a hollow – therefore in a not very strategic situation – next to the stream of Olost and to the south of the town of Olost and very close to its main nucleus, although it belongs to the municipality of Oristà. The castle arose in the 11th century after the disappearance of the castle of Oristà. It started as just a watchtower with a rectangular plan. Later on, it became a castle, although it was never a defense fortress but rather a stately residence bringing together feudal possessions. Of the old building, the tower and the Gothic chapel are currently preserved.
It is located on top of a rocky spur, to the north of the term. The plan of the current complex is trapezoidal and is the product of several construction phases, of which the oldest (15th-16th century) that is preserved in height corresponds to a square tower, dated to the 15th century, located in the East. The rest of the constructions are delivered to the tower and would be chronologically later (16th-18th centuries). To the south-west of the main complex, a square tower (from the late medieval period) is preserved, which is located on top of a hydraulic mill linked to the castle. This tower is given a section of perimeter wall, which would be later than the tower.[1]
The rest of the walls and structures of the medieval construction (except for the aforementioned towers) would be located underground, together with the remains of the evolution and use of the whole complex.[1]
The rest of the building consists of three floors, with a rectangular plan and a roof with a double lateral slope on the facade of the entrance door. The central part of the right facade is occupied by the tower with a rectangular plan and with the crowning with battlements redone in a modern way. Around the castle there are several outbuildings that are used as housing by the farmers.[1]
The well block stands out, built with a cylindrical body made of stone and mortar, currently restored with the addition of cement, flanked by two pillars with an elongated rectangular base that support a wooden beam that acts as the axis of a double-sloped roof with Arabic tiles On one of the pilasters, on the outer and upper part, the date 1678 is preserved.
Info taken from Wikipedia