The port of Mahón has always been a strategic place that for many years has suffered from the siege of innumerable enemy warships. There was a time when it was necessary to use a system to prevent maritime traffic in the area, military strategists needed to have that control at the point of the mouth and that was nothing more than a huge chain that crossed from side to side the roadstead, at the floating height of the boats, and that would stop anyone who tried to cross without permission when entering or leaving.
Attached to the Torre de San Felipet there are two buildings with a semicircular vault that served to keep the chains that closed the entrance to the port, as well as the electric submarine mines for their defense. Later, these buildings were used to protect the projectors of the harbor entrance that illuminated the area to see the approach of enemy ships.
The chains, as can be seen in the plan of the Hispanic Digital Library, prevented the passage by sea from San Felipet to Cala Pedrera and were one more element that was used for the defense of the port of Mahón.