Around 1073, abbot Aldebert II began the construction of a fortified tower-monastery intended to serve as a refuge for the monks facing repeated attacks on Saint-Honorat Island. Listed as a Historical Monument by Prosper Mérimée on the first list of 1840, the tower characterized by the combination of military architecture and various religious inner spaces has become the emblem of the Lérins monastery. Initially defensive, the structure was enlarged and pierced with wide openings in its eastern wall to light up a large room and the Sainte-Croix chapel. It also houses a work cloister on the first floor and a prayer cloister on the second floor. The tower is currently being restored to improve the visit of the monument and finalize its durability.