Dating back to Byzantine times, the castle took its current form in the early 16th century from the Venetians who liked to build their forts close to the sea to command the trade routes. The old fort had been built on the hill at the edge of the Livatho valley. Having fallen in succession into the hands of the Byzantines, the Franks and the Turks, at the end of the year 1500 the Venetians liberated the castle from the Turks with the help of the Spanish and the people of Kefalonia.
For the following four years the Venetians proceeded to restore and fortify the castle walls with the work being supervised in 1504 by the engineer Nicolo della Cimara. A 'borgo' or suburb was built in the front of the castle and this is the area called Kastro. The work was carried out by 40 Venetian craftsmen and local forced labour. The road leading to Argostoli from the castle was named Strata Communa and runs behind the hill which was planned to ensure that it would not be seen by passing ships.
The main street of Kastro led from the castle to the church of the Evangelistria which was built on the other side of the hill. The castle meant security and protection for those who lived in the suburbs and the Kefalonians preferred to be ruled by the Venetians rather than the Turks and were impressed by the knowledge of the Venetian engineers.
The castle was finished in 1545 and its asymmetrical polygonal walls are 620 metres in length. It covers an area of 16,000 square metres and is 320 metres above sea level. The castle is divided into two parts with a horseshoe shaped interior courtyard with a rocky rise at its centre. There are three main bastions with one facing Argostoli, one facing the sea and the third facing the village at the entrance. The coats of arms of various ruling Venetian families can be found on the walls within the castle.
The area around the Castle is well worth exploring with remains of pre-earthquake village houses and the remains of the medieval church of Evangelistria built in 1420. The remains of the church of St. Theodori are located south west of the castle and this church may well be even older than Evangelistria.
The bells of the ancient church are no longer hanging from the bell-tower but are on display outside the church. Some renovation is under way so the bells are being moved.