Built during the War of the Restoration period, the Forte do Cão aimed to reinforce the defense of the Portuguese coast against the threat of the Spanish armada, namely the border area of ​​Minho. The structural typology of this fortress shows evident similarities with the fortifications implanted between Vila Praia de Âncora and Esposende, whose planimetry at the time constituted an advance in the defense and watch system.

Possibly these fortresses were designed by the same engineer, as part of a constructive plan for new fortifications that would reinforce the firing line of the existing fortresses. In the bordering region of Viana da Foz do Lima, there are two fortresses, Areosa and Montedor, which have the same general concept as the Forte do Cão.

The structure of the fort, although small, allows it to be classified as a true fortress. With a starry plant, it has four bastions, two smaller ones joined by a curved face, facing the sea, and two larger ones next to the front space. The elevation of the fort has a very simple and austere structure, with traces of the existence of a counter between the left bastion and the curved face of the rear facade.