In Arcadia, on the slope of the Lykaion Mountains and high above the Alpheios Valley, lies the ancient city of Theisoa. The fortified town was laid out after the Synoikismos of Megalopolis and was again used as a Frankish fortress. The volume presents the archaeological building remains (city and acropolis walls and gates, houses, an Ionic-Doric stoa) and their reconstruction as well as a newly found Theorodokian inscription. The ancient and high medieval history of the site, its location and function in the system of routes between Elis and Central Arcadia as well as its archaeological context in the region are elaborated in detail.