The Castro of Pena Grande features a main circular enclosure with an approximate diameter of 80 metres, located in an elevated position. The settlement is enclosed by a substantial earthen rampart that reinforces its defensive character, while in the western sector large rocky outcrops provide natural protection. The main entrance is located on the south-southwest side, allowing strategic control of access to the site.
In the northeastern area, an outer enclosure (antecastro) has been identified running parallel to the main defensive system and also bounded by an earthen rampart. This area likely functioned as a complementary space for the settlement, expanding the inhabited surface and activity areas of the community.
The complex is completed on the southeastern side by a defensive system consisting of three ditches and three parapets, which increase the structural complexity of the site. This combination of ramparts, ditches and parapets reflects the strategic importance of the settlement during the Iron Age, as well as the sophistication of the defensive techniques employed by its builders to protect both the population and their resources from external threats.
