The Tower, with its complex stratigraphy, is an exceptional example of Norman military architecture; it has a square plan with a base side of 8.25 meters. On the ground floor, there is a room (made accessible in 2024) with a side of 3.25 meters. On the second level, which starts from a majestic projecting stone cornice, probably marking the elevation commissioned by abbess Febronia in 1152, there is a square ‘cell’ with a side of 3.8 meters covered by an interesting cross vault; it was accessed from the female monastery via a step-ladder, designed to make the room inaccessible in case of danger. Today you can visit it via the access walkway designed by architect Verderosa in 2007 The first abbess Febronia is credited with the erection in 1152 of the tower that bears her name, as can be seen from the inscription on the lunette of the architrave of the single-light window on the first level: “+ Anno ab Incarnatione Domini - Anno Millesimo Centesimo Quinquagesimo Secondo – Indictione XV (sic) – in tempore Domina Febronia Abbatissa fecit opera ista”. ‘The unusual position of the Febronia tower, offset from the contemporary church, suggests the hypothesis of a pre-existence so significant symbolically or constructively that it induced the first builders of the monastery to disregard the alignment of the fortified redoubt with the adjacent religious structure.’ (Luigi Guerriero).