I used to be station in eastern Germany in a base close to some old NVA missile silos. Sometimes we would go jogging or biking through there, and just go spelunking if we felt like it. Also a good way to cool down in the summer. Everything was rusted and all the places that were easily accessible were smeared with graffiti. They sealed it off now, welded the doors shut and everything.
Sometimes you would find old 7.62x39 blank cases lying around in the forest around there too. A comrade of mine even found a loaded cartridge once. Not sure what came of it though. If he had reported that incident the area would probably be fenced off now, since we take UEM very seriously.
Sadly I didn't take any pictures, but you can easily find some on the internet.
Pic related. Nowadays the green doors are welded shut. There are also some other tunnels, trenches and bivouacking spots around there. You can even see where they dug their foxholes. It's fascinating to me. I remember all the times I have sat in my hole and thought about home. Sitting in the spots these guys used to sit in really does make you contemplate why you do what you do.