Peenemünde!
The biggest factory and research facility for special weapons like the V1 and V2.
The museum inside the old coal power plant is huge. The exhibiton guides you through the ages from WWII, first space craft´s like the russian "Sputnik" till now. Outside are some aircrafts, helo´s, rockets, a missile speedboat "Tarantul" and a soviet SSG Juliett-class....
You really need a whole day there
Peenemünde military test site