Mourão Castle was built in the early 14th century, in 1343, during the reign of King Afonso IV of Portugal. Erected at the highest point of the town, it was constructed using local schist masonry, as well as marble and granite. The castle has a rectangular layout, reinforced by six square towers, and is accessed through two gates: the Keep Gate (Porta de Menagem) and the Gate of the Black Tower (Porta da Torre dos Pretos).
Due to successive wars, the castle required major reconstruction around 1661, with support from the City Council of Évora. Around 1663, the architect João Nunes Ticono initiated a comprehensive restoration plan, which led to the construction of six watchtowers (atalaias) placed on elevated hills to protect the fortress, particularly along the direction of the Guadiana River.
These masonry watchtowers, now in ruins, are located at the following sites: Atalaia de Cuncos, Atalaia das Ferrarias, Atalaia da Meada Alta, Atalaia do Meio, Atalaia da Abegoaria, and Atalaia da Coxa.