Yet another magazine I read is Budget Travel. I wish they were a bit bigger but their premise is that EVERYONE should travel and because of their open audience you find fewer ads for Hermes and Cartier. Both brands I will likely never own in my life. I can barely afford knockoffs.
Their December/January issue had a notice about a list on their website budgettravel.com that finds the best Underground Tours in the World.
A Nazi hideout
An ordinary door in Berlin's Gesundbrunnen train station leads to an abandoned air raid shelter that reveals Berlin's dark underbelly: an array of secret bunkers, escape tunnels—even an aircraft factory—built by the Nazi regime during WWII and expanded during the Cold War. Berlin Underworlds' Association, 011-49/30-4991-0517, berliner-unterwelten.de, 90-minute tour $13.
My son would LOVE this so it's definitely making the list of things to do. They offer several options and I'll let him decide which one we will do.
Craig and I went on an Underground tour of Rome with Context Travel (have I praised them enough because I LURV them)
I was sure to vote for them when they were a finalist for NATGEO's awards.
Context was also kind enough to recommend a person to contact in Germany who might be able to create a private tour for my son and me. I'll post if anything turns up with that.