It predominates over the Sado valley, the hilltop on which it was implanted was successively occupied since the 6th century, becoming an important urban and military centre on the Moorish peninsula.

[2][3][4] Archeological excavations occurring in the 20th century, proved that Alcácer do Sal was constructed during the Almohad Caliphate, during a period of Moorish occupation in the Iberian peninsula.

[2] It was conquered in 1158 by D. Afonso Henriques, but was retaken in 1191 by the Arab Moors, as evidenced by the construction of the pentagonal tower during its occupation.

[2] The unstable accessways along the walls were reinforced in 1971, along with repaving the foundations, filling of cracks along the parapets and the masonry (to imitate the taipa removed from the site).

[1][2] A public tender was issued in 2000, to award a contract to secure and reinforce the hilltop (Diário da República, Série III, 215, 16 September).

[2] At the same time, work began on setting-up the Special Protection Zone (ZPE), by the municipal authority of Alcácer do Sal (September 2003), supplemented by a similar act on 16 May 2005.

[2] The castle is located on a hilltop on the edge of the rural area of Alcácar do Sal, isolated over the town, river and adjacent terrains.

[2] To the north, alongside the cloister centred on a two-storey wings, encircled by rounded arches over pilasters, with upper-story framed windows.