This defensive terrace, built in the modern era, was designed to support heavy artillery positions. Its construction partially masks the original structure of the Tower of James I. The arched doorway you see in the wall to your left is the original entrance to the tower, which was intentionally built high above the ground to make access difficult during an enemy attack.
Cannons were brought up to this gallery using a ramp, and three embrasures are still preserved here. Looking south from this point toward the nearest hill, you can see the remains of the Fort of Santa Quiteria. It was built in the modern era over the ruins of a thirteenth-century chapel dedicated to that saint.
The fort served to support the castle from a slightly higher vantage point—a position that absolutely had to be fortified, as an enemy army could use that hill to bombard the main castle with a distinct advantage.
It is worth remembering that Monzón Castle endured brutal sieges during modern conflicts, including the Revolt of the Catalans, the War of the Spanish Succession, and the Peninsular War. It was targeted relentlessly by enemy artillery fire and shaken by numerous underground mines dug by attackers attempting to collapse the fortress walls.