[1] Legend suggests that during the 2nd century a castro was taken and colonized on the hilltop of Mons Sanctus, by Roman Praetor Lucius Aemilius Paullus.

Beginning in the 1476, the area was reconstructed during the reign of King D. John I, resulting in the construction of a barbican and protection over the well, a large 15 metres (49 ft) chamber that belonged to the Castro family (later identified as providing abundant water for the site).

[1] At the beginning of the 16th century, Duarte de Armas conducted a graphic survey for his Book of Fortresses, designing the castle with two access gates (the oldest opened to the cliffs) and protected by two towers.

[1] In the second half of the 17th century, the structures were adapted to support artillery, with the construction of earthenworks, batteries and canon emplacements, as well as fortification walls for the colony.

[1] An 1831 collapse of a cliff resulted in the destruction of an exterior wall and a time when the Chapel of Santa Maria was in a state of ruin.

[1] In 1986, complementary work continued in the castle area that included repairing loose ashlars and consolidation of the pavement along the adarve in the west.

[1] In the east, is a lookout to the eastern frontier, with the south and southeast overlooking the valleys of Ponsol and Aravil, in addition to the Cerro da Cardoza.

[1] The walled enclosure, adjacent to the main entrance, features a rectangular outline and a full arch door inserted in the south section, that includes battery with four canon emplacements, equipped with two ramps.

[1] Inserted into the western side is an irregular oblong segment with full arched door and protrusions that integrates a square-shaped tower on the exterior.

[1] The Torre do Pião is located outside the walls, in an elevation bordering the castle, overlooking the ruins of the Church of São Miguel.

[1] The Gate of Santo António, faces the west, and includes a straight lintel integrating laterally three gaps, surmounted by the royal coat-of-arms and topped by small parapet.

Addorsed to the gate is a square guard tower covered in stonework, with door of straight lintel in the east.

[1] The battery over the parking area, in Largo do Baluarte, is trapezoidal, with curtain walls over the escarpment, with door and flanked by two rectangular windows in the west.

[1] The Chapel of Nossa Senhora do Castelo is located inside the walls, next to the battery, with longitudinal plan and comprising two juxtaposed rectangles.

Its main facade (to the west) is delimited by Tuscan pilasters, torn by a hollowed arch portal with protruding stone and flanked by a small quadrangular opening and gable with cornice.

Its main facade is oriented to the west, and includes full arch door with four archivolts, imposing towers and capitals with zoomorphic decoration.