It occupies the site of an old 13th century Templar fortress of which no vestiges remain. In 1334, King Afonso IV, son and successor of D. Dinis, began the construction of this walled enclosure within the ramparts, culminating in a keep. In 1488, João II ordered the reinforcement of said keep, which then became the highest in the area.
The Castle is a beautiful example of the military architecture of the time. It has a trapezoidal shape with a central courtyard and three cubic towers at the corners, in addition to the keep, located to the northwest, from the time of D. Afonso IV, son of D. Dinis.
The keep, 37 m high, stands out from the rest, being the highest of the fortress towers in the Spanish-Portuguese border. Built in masonry reinforced by stone ashlars at the corners, it has 24 arrow slits that illuminate its interior. At the top of its four faces, you can still see the remains of the primitive machicolation that defended its flanks, one of which was rebuilt in reinforced concrete around 1973. At the foot of the barbican, a moat was dug, ordered by D. João II in 1488, completely surrounding the fortress.
The Castle houses part of the González Santana Ethnographic Museum.
The keep has three rooms inside. The upper room stands out, with a beautiful ribbed vault. Today 17 ramps lead us today to the terrace, from which we can see the city of Olivenza and the Spanish and Portuguese countryside and surrounding towns. In ancient times, it allowed artillery pieces to climb to the top, so you can see the corners are lowered at the bottom. The lower room holds today an exhibition of Medieval gaffiti.