The Kilia stone citadel (in fact, New-Kilia, today Kilia, Ukraine), located on the left bank of the northern branch of the Danube, was the oldest and most protected part of the medieval defensive ensemble. Most likely, it was built by the Genoeses that had their own colony, ruled by consuls in the second half of the XIV century. In order to supplement the data on the Kilia citadel (which does not exist today), the author uses the Ottoman and Russian topographic, iconographic and graphic sources of the late XVIII century. The citadel was a quadrangular fort, separated from the rest of the fortified complex by two ditches filled with water. The corners of the stone square were reinforced with four parallelepiped towers: the Commandant’s Tower (Dizdar Kulesi), the Agha Tower (Ağa Kulesi), the Ammunition Tower (Tophane Kulesi) and the Arsenal Tower (Cephane Kulesi). The Kilia citadel perfectly illustrates a mixed (combined) or transitional model with one or two peripheral donjons, with equal defense capabilities from all sides. It is based on a regular Italian quadrangular castle with four corner towers in the form of a parallelepiped.