The medieval tower, located at the highest point of the village, is a unique attraction for tourists seeking spectacular views of the Comino Valley. Its imposing size and prime location on a rocky outcrop make the Tower of the Counts of Aquino an unforgettable experience.

The Tower is the ancient symbol of the village. Built in the 13th century when the warlike Counts of Aquino became feudal lords of San Donato, it is outside the fortified village (Castrum Sancti Donati), thus isolated from the remaining dwellings in the castle. The location, structure and position of the observation points served to ensure control of the Via Marsicana leading to Abruzzo, as well as a secure defense for the castle's notable in case of attack.

Square in shape (dimensions: 5.40×5.40×12 in height), there are no entrance doors, which suggests that access was through a south-facing window located almost at the top of the Tower by means of ladders or ropes. It was originally higher and protected by battlements.

The Tower, built and oriented according to the declination of the Sun, still shows us the four cardinal points, the direction of the Abbey of Montecassino and the position of the Sun on the day of the equinoxes and solstices, like a compass. An ancient legend tells of an underground tunnel that connected the Tower to the crypt of the Sanctuary of San Donato and guarding it was a fearsome dragon.