Thun Castle (German: Schloss Thun) is a castle in the city of Thun, in the Swiss canton of Bern. It was built in the 12th century, today houses the Thun Castle museum, and is a Swiss heritage site of national significance.The castle was built between 1180 to 1190 by Duke Berthold V of Zähringen, who constructed the still preserved keep to the level of the Knights' Hall. In 1218 it was inherited by the House of Kyburg, and 1384 it was taken over by the Canton of Bern.