The paper describes the seismic vulnerability assessment of ancient water towers, part of the aqueduct system of Pompeii. For this work the archaeological findings were used which were brought to light after in-situ and laboratory research. For the seismic vulnerability assessment the first step was the kinematic analysis of twelve water towers with different height and slenderness. Following, one tower was selected to be modelled in the finite element software DIANA. Pushover analyses with uniform and 1^st mode force distribution were carried out for the safety verification. The same pilaster was used for the two-dimensional discrete element analyses with the software UDEC. The scope of this was to simulate the rocking behaviour during different seismic scenarios in order to investigate the overturning probability for different levels of seismic excitation. Finally, it was investigated the additional vulnerability that a bad masonry condition, due to the lack of masonry blocks or mortar, can create. Based on the results of this work, it was decided if it is necessary or not the strengthening of the analysed water tower.