Just a few minutes from where I live is Bahnhof, a former nuclear bunker, most famous for having hosted Wikileaks. It is built 30m down, in 2-billion-year-old solid rock which can withstand a hydrogen bomb. The doors are 40cm thick. It has waterfalls, plants and a 2 500 litre fish tank.
Even if you look through the doors from the street it looks like something from a movie! Read more here