Mysterious Cubus in Bremen, Germany

During one of my latest trips I discovered this huge concrete building in a Forrest next to the city center of Bremen, which is one of Germanys greater cities in the northwest.

I have no idea what function this building has or had, but it makes a pretty good motif if you ask me. It somehow reminded me of that old, trashy horror movie called "cube" - where rooms inside a giant cubus move and thereby terrorize their residents.