La Coupole is one of the most effective and exciting centers dealing with World War II and the subsequent Space Race. It's a huge dome of concrete housing a vast network of 7 kilometers of underground galleries near the north French coast just 5 kilometers from St. Omer in Nord Pas-de-Calais. It was designed in 1943-44 by the Todt Organisation, responsible for major works for the Nazi state, and built by Allied prisoners in appalling conditions. The sinister construction was intended as a launching base for V1 flying bomb and V2 rocket attacks on London. In 1944 the Allies discovered its existence and undertook a successful and massive bombing campaign and the place was abandoned.
From the summer of 1944, it lay empty until it was decided to turn it into a museum. In 2010 La Coupole was renovated once again and now it is as much the story of the space race and how it came from the horrors of World War II as the war itself.
If you visited before the renovation, go again. Together with the new films and interactive displays, there's also a very good audio system. Pick up an audio guide in your language (free with admission) which turns on automatically beside each exhibit. The audio guide also works as you are watching any of the four major films, and I urge you to try to see all four if you can.
This is one of the most intersting and impressive exhibitions (it's more than a museum) that I have seen in a long time.