The Lettenberg is a smaller hill (79m) at the side of the Kemmelberg, which is located at the Lokerstraat in Kemmel. Towards the end of 1916, the British Engineers and Tunnelers started with the excavation of underground headquarters on the Kemmelberg, which was the most important British observation post. Between April 4th and the end of May 1917, the 175th Tunneling Company worked on a brigade headquarters under the Lettenberg. The concrete bunkers that gave access to this headquarters have been opened again in 2004. Included are five shelters, built in reinforced concrete that were poured in rough gravel on corrugated plates, each with an entrance and a window opening on the western side. Access by way of a footpath with information panels is free of charge.