A cylindrical tower capped by a semi-dome in the north corner of the reservoir; the tower does not exist anymore. It also contains putlog (scaffold) holes. However, unlike the Fildamı tower, this tower has no indication of the existence of an internal cylindrical chamber. Excavations made to a depth of 5,5 m below present ground-level revealed no channels. It is unclear how the reservoir of Aspar (and Aetius) reduced the water pressure in their earliest outflow systems.
The tower presumably served to reduce the pressure of water exiting the reservoir, but the absence of channels at the bottom and the spiral staircase in the outer chamber like Fildamı makes this identification less certain. The tower was built beside the north-west wall of the reservoir, and if the location is significant, it is possible that the water was used to supply the north-west of the city, that is, the area around the Blachernai Palace (Crow et al., 2008, p. 131).
The position of the tower on the north-west wall may imply its relevance to supplying that part of the city, the area around the Blachernai Palace. Repairs in the recessed brick technique at the south corner suggest attention in the 10th century, although it is not certain whether this was because it was in use or whether the area was put to a new purpose such as market gardens (Crow et al., 2008, p. 131-132).