Antirrio played an important role in the Byzantine and post Byzantine era due to its strategic position. Antirrio followed Nafpaktos’ fate, when it was surrendered in 1499 during the first year of the Venetian Turkish war.
It was then that Soultan Vagiatzit II realized the strategic significance of the «strait» and secured the entrance with the construction of two forts on both capes (Rio of Moria and Rio of Roumeli), on ancient foundations. The channel of Rion was named during the 17th century as Dardanelia of Nafpaktos, Antirrio was also named as Kasteli of Roumelis, while the opposite Rio Kasteli of Moria for their powerful position.
Today, the medieval castle has been restored by the Ministry of Culture and it is used for cultural events during the summer months.