The castle was built by the Ottoman Sultan Bayezid II in 1499 above the ruins of an ancient temple of Poseidon, within three months.

Along with its twin, the Antirrio Castle, they were intended to protect the entrance to the Corinthian Gulf, and were nicknamed the "Little Dardanelles".

The Venetians rebuilt the castle, restoring and strengthening it by the addition of towers, giving it its final shape.

The Ottomans retook it in 1715, and remained until they surrendered it to French General Nicolas Joseph Maison.

Between 1831 and 1912, the castle was used as a military and then civilian prison, whose inmates were often used by the municipality of Patras for cleaning the streets of Rio.