It was the first bastion to be completed, located where the small fortress of Santo Cristo de San Román once stood. The designs for the bastions, moats, and rebellines were probably by Sergeant Major Pedro Osorio de Cervantes, and the work was directed by Jaime Frank, who equipped it with thirty pieces of artillery. It is built with saskab stone bonded with a mixture of seashells. In 1963, it was used as a craft market and later as housing for soldiers' families, who caused damage to the building as it had no sanitary facilities, turned the rooftops into rubbish dumps, and ripped up the floor tiles.