It is located on the top of a tree-lined hill in the west of the modern city, near the shores of the Amvrakikos Gulf, 9-12 km east of Aktio airport and the city of Preveza. It was built in the early Byzantine period (probably 9th-10th century). Already from this period, Vonitsa is an important fortified city and functions as a basic trade center between Acarnania and Epirus, as an important naval station, but also as a seat of Bishop. The city flourished in the 11th and 12th centuries and the emperor Alexios Komnenos endowed it with special privileges. After the Fourth Crusade (1204) the area it came under the Despotato of Epirus. From 1294 to 1479, the castle followed the historical course of the town, and came under the control of Angevins, the Orsini, the Tocci, the Duces of Lecce and the Knights of Rhodes. After this it came under Ottoman (1479-1684) and Venetian rule (1684-1797). In 1798, the town and the castle passed into the hands of Ali Pasha of Ioannina, were liberated temporarily in 1825, and were finally incorporated into Greek State in 1829.
The castle of Vonitsa has an ellipsoidal shape and is articulated in four defensive zones. The wall is preserved to a height of 10-12m., reinforced by square towers and ramparts that have a number of holes for cannons, while at the upper level there is a peridrome with parapet and bastions. Variety in the form of walls and towers suggests various building phases, of different eras and influences, covering the entire history of fortifications from the Byzantine era to the late Ottoman occupation.
The lowest southeast zone is the modern access for the castle with a gate and a pointed two-storey tower who protects it. The second zone includes a small area in front of the entrance to the main fort (it served as a front wall). These zones may be dated to the Byzantine period and probably incorporated into the later Venetian defences, which gave the castle its present form. The third defensive zone is the most internal area, on which the majority of the buildings are preserved. The fourth zone is the highest fortified part of the castle. Has the form of an independent internal citadel and may be dated to the late Ottoman period. There is a rectagular building, known as Kazarma, which was probably originally a Catholic church.
Most of the buildings that are preserved inside the castle date back to the late Venetian occupation, except for the cross-shaped church of Hagia (Saint) Sophia, dating from the mid-Byzantine period (10th century).