About the antiquity of the Castle of Lamego, almost all the authors refer that the castle "is the work of the Moors" and prior to the foundation of nationality. From the primitive, only the keep (12th century), part of the old wall and the cistern (13th century) remain.

The donjon, about twenty meters high, is square in shape and has slits of light on its faces, some of which were altered in the 16th century to be turned into windows, by order of the last count of Marialva, D. Francisco Coutinho, perhaps in order to give the tower a housing function. It has a square of arms in the shape of an irregular hexagon, whose wall, with about ninety meters of perimeter, is equipped with an adarve, accessible from the north side by a flight of stairs.