Le Blockhaus d'Eperlecques
In late 1942 Albert Speer asked his experts to find a suitable site for the launching of V2 rockets towards England. Allied agents first noticed suspicious activity in the woods near Watten in April 1943. Vast trenched were being dug for the foundations of a grotesquely monumental building. After the foundations, the next thing built was the roof, a fifteen-foot thick slab of reinforced concrete weighing 37,00 tons and designed to be bomb-proof – which, at that stage of the war, it was. Thousands of slave labourers were shipped in by the Todt organisation in cattle trucks along a specially-constructed railway system. Once the roof slab was poured, it was lifted by hydraulic jacks a metre at a time, and the walls poured under it. In the end, the thing was 28 metres tall and had used 120,000 cubic metres of concrete. Along with neighbouring la Coupole, it became the most westerly launching place of the V2. At this point, Allied bomb technology reached to stage at which serious damage could be done, both to the building and, alas, to the hapless deportees working on it. The Blockhaus was demoted from V2 launching site to liquid oxygen factory, and was eventually captured by Canadians in September 1944.

It is now open to the public, and shows also examples of the V1, not a rocket but a pilotless jet plane, which was in fact never part of the operation at this site.