Tons Of Rock Festival. The Tons of Rock Festival will take place inside the fortress walls itself, giving both the audience and the artists a unique experience. Close to the Swedish border and overlooking the beautiful city of Halden, Fredriksten Fortress was built in 1660. Among many historic events, the most famous is the battle in 1718 - where the legendary Swedish king Charles XII was killed. tonsofrock.no plus.google.com/communities/109518607469934623612