Small coastal fortification, part of the defensive line between the Douro and Minho rivers. It is located on a rock formation whose peculiar shape gave rise to the popular name "Castelo do Queijo" (Cheese Castle). It has an irregular trapezoidal plan, surrounded by a moat. A raised rectangular platform is topped by pentagonal sentry boxes at the vertices. The main portal, in a perfect arch and surmounted by the national coat of arms, was preceded by a drawbridge. Access is through a vaulted tunnel with lateral loopholes. The interior includes an atrium (later covered), a bar, a powder magazine with a barrel-vaulted roof, and stairs and ramps leading to the upper platform. There are niches with granite statuary (São Francisco Xavier and Nossa Senhora). The popular name, derived from the rock, illustrates how local toponymy, based on a striking physical feature, can prevail over the official designation, reflecting the community's perception and appropriation of the monument.