The 'Lettenberg' hill is a spur of the much larger Kemmel Hill, which was the most important British observation post in the sector. Towards the end of 1916, the British engineers and tunnellers started to excavate an underground headquarters complex at Kemmel Hill. The concrete bunkers which gave access to this headquarters have now been restored. There are four shelters, built in reinforced concrete. Access to the site is via a footpath.
Open daily. Free entry.