The castle is built on a low hill. The core was probably constructed between 1231 and 1267 by Michael II Komnenos Doukas, the ruler of the Despotate of Epirus. This is indicated by a monogram in brick on the third tower to the right of the main gate. The castle incorporated a section of the walls of ancient Ambracia, visible on the opposite side of the castle’s main entrance. The river Arachthos used to flow along the line occupied by the modern bypass road, so the east side of the castle was protected by its waters. The defences on the other sides consisted of an inner wall (it survives complete) and an outer wall to protect the base of the inner from siege weapons. Only half of the outer wall survives and it is significantly lower, so as not to impede the field of fire.