The defensive tower, almost 24-meters high, is one of the most impressive in Agios Oros. The compact, rock-bearing, square structure has four floors, two of which are vaulted, and the walls are two-meters thick on all sides. On the third floor, there are machicolations, from where the defending monks threw hot water or oil on the attacking pirates, and around the roof there are ramparts to shield the defenders. The tower was built in 1520 by the Wallachian Voivode (Prince) Neagoe Basarb, according to the well-crafted dedicatory inscription that is visible on its southern side.
