Longis is a settlement in the south east of Alderney in the Channel Islands, with a beach, island fort, nature reserve, and remains of German, Roman and prehistoric occupation. Longis nature reserve is the largest nature reserve on the island, with an area of 103 hectares. Longis Bay Beach is a popular tourist spot. It has an anti tank wall from the Second World War. This massive, concrete structure curves right around the bay above the high-water mark and was built by the Germans during the Occupation of the early 1940s. There is provision for an anti-tank gun in the middle of its length (long since removed).