You have to stoop to enter the dark, dripping tunnel beneath this Neolithic burial mound that leads to the funerary chamber. The dolmen is over 6000 year old, topped with the 12th-century Chapel of Notre Dame de la Clarté, restructured and renamed the Jerusalem Chapel in the 16th century. Watch the introduction film at the visitor centre and visit the excellent on-site museum that displays treasures from the world's biggest coin hoard, found in 2012 in a Jersey field.
Walk around the mound to enter the German battalion bunker – part of the Nazi fortifications created using slave labour during WWII. It houses a moving memorial to the prisoners of war who built it.