Thun Castle was built at the end of the 12th century by the Dukes of Zähringen as a grand castle complex with a mighty donjon (central residential tower) overlooking the town. Later, the Kyburg and Bernese extended the complex, resulting in the tower with its four distinctive corner turrets and imposing roof, which today stands as an architectural landmark high above the Aare river and the old town of Thun. Inside the donjon, a circular route takes visitors through five museum floors featuring historical exhibitions. The historically significant knights' hall is one of the largest intact banquet halls of the High Middle Ages in Europe.