One room even features a secret entrance — hidden inside a rocket by the pool. — Ey — pshhh! :-)

I used to live in the inner city of Leipzig during my university days, and we had a door in the basement that led to wartime tunnels connecting it to other houses. It wasn't like a massive maze, just a hub with three other paths, each leading to another house nearby. From there, however, if they'd unlocked their doors, you could travel farther.

I was on a mission back then to befriend and convince random neighbours across the street to open their access doors and get some kind of network going, but I didn't meet with much enthusiasm.