In the United States, The National Park Service land; NPS policy "does not allow for battle reenactments (simulated combat with opposing lines and casualties) on NPS property. There are exceptions i.e. Sayde or the Schloss Kaltenberg knights tournament. The majority of combat reenactment groups are battlefield reenactment groups, some of which have become isolated to some degree because of a strong focus on authenticity. The specific German approach of authenticity is less about replaying a certain event, but to allow an immersion in a certain era, to catch, in the sense of Walter Benjamin the 'spiritual message expressed in every monument's and every site's own "trace" and "aura"', even in the Age of Mechanical Reproduction. Historic city festivals and events are quite important to build up local communities and contribute to the self-image of municipalities. Events in monuments or on historical sites are less about the events related to them but serve as staffage for the immersion experience. In Denmark several open air museums uses living history as a part of their concept. These include Middelaldercentret, The Old Town, Aarhus and Frilandsmuseet.