On the former sand dune Langlütjensand an island was built in 1869/1870, which was built with earthworks to a fortified coastal fort (♁53 ° 33 'N, 8 ° 31' coordinates: 53 ° 33 'N, 8 ° 31' O | OSM |) , Of the construction works are only available to Langlütjen I lore, which should be equally valid for Langlütjen II. The cost of Langlütjen I was estimated at 300,000 Taler before construction, the actual amount is not known.
About 300 men worked at the plant at the same time. The procurement of all building materials for the work begun in 1869 took place by ship. From 1870 served to the still existing dam on which a narrow-gauge railway with a gauge of 837 mm reversed. During the low tide, the site was about five hours in calm weather and only two hours free of water in rough seas. The work could only be done from March to December. 112,000 oak piles were driven into the subsoil. The foundations contain 300,000 bundles of shrubbery, 2,700 m³ of rubble and 1,900 m³ of sandstone blocks from quarries near Hameln and Springe.
Upon completion, the fort received nine 21-cm guns in armored towers and was used until the end of World War I, but has never been involved in combat operations. After the war, a demilitarization took place and the armament was removed by the victorious powers.
During the Second World War, the armament was switched to anti-aircraft positions with 10.5 cm guns in newly erected concrete gun stands. The plants were blown up after the war and the remnants of debris in the 1970s for reasons of coastal protection washed over with sand. However, fragments of debris still stick out of the sand. The island is connected to the mainland by a 1.6 km causeway. In addition to the dam, a radar tower for Weser shipping was built near the island in 1983. The north shore of the island was badly affected by the flood of All Saints in 2006. The concrete bank was washed under and the plates were pushed over each other. At the Erdaufschüttung created steep bank areas.