Tower built on the exterior of the reservoir to reduce water pressure. The tower has an 1 m-wide entrance at the east wall. On the inside, it consists of concentric chambers, with a central shaft (1,10 m in diameter) enclosed by an internal spiral staircase of 0,80 m wide. The channel from the main reservoir led into the outer chamber with the staircase (Crow et al., 2008, p. 136-137).