The castle was very close to the border between Guyenne and Languedoc, and that border was bitterly fought over during the Hundred Years’ War. There are only a few remnants of the medieval building, which used to be called “Château de la Tour” (Tower Castle): a huge vaulted cellar, large enough to accommodate a few dozen horses; a cistern; an oven; the two towers that guarded the fortified gate; and part of the fortified wall.

The urbarium, the first land register for Mondonville, allows us to picture the stronghold as it stood in the Middle Ages.

It was intended mainly as a defensive building, sporting an impressive keep (12 metres wide, 35 metres high) surrounded by a 6-metre high outer wall with a deep moat to the south, along which the village houses huddled together. A strikingly large well, 2,2 metres in diameter, still stands in the middle of what used to be the courtyard. It provided the town with water in the event of a siege.
The new building, which was erected in the 19th century (1823-1830) exhibits a classical architectural style: the main part of the building, two floors high, is flanked by two terraced wings with no upper floors.