In the seclusion of the island of Usedom, near the fishing village of Peenemünde, the Luftwaffe and the army built two independent test facilities for liquid-fuelled rockets and other revolutionary military innovations in the strictest secrecy. In 1937, construction began on the world's largest rocket research centre until the end of the war, at a cost of over 10 million Reichsmarks. During the war, this "cradle of space travel" housed over 20,000 technicians and workers at times. The facility's most famous development is the V 2, which has gone down in history as the first long-range rocket.