Like almost all first-tier fortifications, it metamorphosed over time, seeking to respond to new war technologies. The bastion fortification then reinforced the entrances to the urban fence - Portas de Ródão, Portas da Vila and Postigo do Torrejão - while reinforcing the defense of the Castle in its most vulnerable area: the continuation of the crest to NO. Given the orographic characteristics of the place, the defense of the fortification would only need care in a small number of points. Thus it was thought, still in 1801:

Marvão is a very strong square by nature: built on high and almost inaccessible rocks, it reduces its defense to a small number of points that must be improved, and carefully kept, and that through an ordinary, but effective surveillance in the precise places, in around the remaining circuit of the Square, this can be made impenetrable to the violent and bloody attempts of its enemies.