Situated in one of the most fertile areas between Lagos and Sagres, exploited since at least the Roman period, the fortress of Quinta das Alagoas was a modest but essential protagonist in the western Algarve coastline defence against pirate boats that went up the river Ribeira Vale de Barão, navigable before the 1755 earthquake from Boca do Rio (known at that time as Almádena Beach) to Almádena.

The central building of the fortress, whose construction is probably dated from the end of the XIV century, develops as a square with remnants of a tower in the southeast corner plant. A loophole on the east side of the entrance gate can still be seen as well as embrasures in opposite walls of the courtyard. An inscription in ancient humanistic style can reveal the date of construction: 1364. The squat form with low but very large walls with a bastion tower and two embrasures on the lower floor seems to reveal the incorporation of the principles of active defense and adaptation to the new firearms of the military architecture that emerged at the end of the XIV century.

According to oral tradition, many watchtowers have collapsed by fire or by the 1755 earthquake, but the fortress of Alagoas survived due to the robustness of its foundations on the rocks where is built. It lost the main tower, small watchtowers of which there are still traces in the corners of the wall over the entrance arch and the merlons referenced by reports that are transmitted from generation to generation.

Two of the adjacent building structures (currently referred to as “barn” and “stable”) retain their original walls but there is a mixture of construction materials visibly picked from other sites. Examples of this are two small stone pillars, in renaissance style, probably reused from an earlier construction, to strengthen the doorway of the stable.

Apart from a Neolithic ceremonial ax found in the garden, the oldest traces in the farm are probably a weight of a mill and a brick archway at the base of the north wall of the water mine, which may reveal a possible Roman origin.

The building was in a state of great decay, and reconstruction work started in 2004, stopped that year to eventually continue from 2012.