The use of this room as the Palace prison has documented records that date back to the early 17th century, although its construction coincides with the entire complex. As mentioned earlier, the access is currently located inside the public service desk.
In its interior, there is a set of graffiti drawings with zoomorphic, anthropomorphic and naval representations which is one of the monument’s most original artistic creations. Likewise currently covered by a grille, a network of tunnels was discovered which were excavated in the substratum to capture water from the ground-water level. Before entering, there is a set of incisions on the wall in the form of knives or daggers accompanied with a crucifixion image.