The function of the towers was primarily defensive, and for that reason it is surprising to find this one inside the structure of the building complex. This is a consequence of the many alterations and enlargements the Dockyard has undergone throughout its history. It maintains the Gothic architectural style prevailing at the time it was built, with the typical pointed vault formed of two crossing ogive arches.
Of the four towers that were built in the thirteenth century, only two survive; those not affected by the great reconstruction that the building underwent during the sixteenth and seventeenth centuries. The remains of the other two have not been found but must have been near the existing Customs house on the other side of Josep Carner Street.
The tower has embrasures and merlons; the embrasures are windows which are very narrow on the outside but wider inside, in order to facilitate shooting arrows for the defenders, at the same time as protecting them from missiles. The merlons are rectangular blocks placed at regular intervals on top of the tower which allowed the defenders to shelter from enemy attacks.