The Castle of Nafpaktos is one of the most representative monuments of fortress architecture in Greece. It dominates the area, standing imposing on a hill, in a location of great strategic importance that enables us to watch over the Rio-Antirio narrow strait, at the entrance to the Corinthian Gulf and in the middle of the Ionian Sea. It is the most important monument of the rich and eventful past of Nafpaktos, as it was the core from which the town evolved. The successive construction phases from classical antiquity (5^th – 4^th century B.C.), which date back to the first structures of the fortification, are still visible today, to the byzantine years and finally to the Ottoman interventions, mainly in the 17^th century and 18^th century, then dictated by the use of firearms. In its present form, with the total perimeter of the external walls being 2,250 meters, it is an important example of a Venetian fortress of the 15^th century (1407-1499), when the city was an important commercial and naval hub. Built amphitheatrically, it encompasses the top of the hill (castle citadel) and the hillsides down to the sea. From there, two piers follow the natural morphology of the ground and descend east and west to close the entrance to the harbor. Transverse walls unite the two piers and form five defensive zones (tiers) from the hilltop to sea level. The castle has four gates around its walls (only three survive today) and the Venetian Sea gate, while each transverse wall has a gateway to the next tier(rampart). One of the most distinctive gates is Sideroporta(connecting the lower city to the upper city). A Venetian gate, which is maintained in the area with the impressive Venetian murder-hole and the embossed decoration of the Italian Renaissance-style to protect it. The traditional settlement of Nafpaktos is surrounded by the first two tiers from the sea level and brings to life the image of a true fortress state. The first tier, named “lower city -Kato Poli”, surrounds the small Venetian harbor and the mansion of the Demetrios and Egli Botsaris Foundation, which houses a museum dedicated to the Lepanto Naval Battle. The second tier, named “upper city – Ano Poli”, encloses the area of Vesir Mosque with the restored mansion of the Tzavela family and the complex of Ottoman baths and higher, on the slope of the tier, the independent bastion “Ntapia Tsaous”, constructed during the late Ottoman period with a horseshoe shape and toothed bastions (ramparts), specially designed for the use of large firearms, which prove very interesting to the visitor. The third tier features a triple monumental gate, which is the entrance to the archaeological site. A cobblestone path leads from the low gate to the acropolis (fourth and fifth tier). In almost the center of the fourth tier, we find the chapel of Prophet Elias, 19th century). It is built on the site of an Islamic mosque, which in turn was built on a Byzantine temple, as illustrated by embossed marble inserts with animal and plant representations. The fifth tier (upper Citadel or Its Cale) is the best protected part of the castle during a siege, as demonstrated by the recently restored vaulted rooms, the small escape gate and the water tank. Walk along the cobbled footpaths, follow the perimeter of the walls and discover the ambience of the old fortress town, in one of the most impressive and well-preserved Venetian castles in Greece!