We arrived to the hotel in the early afternoon, grabbed lunch, and then went to an Unterwelten tour (which literally translates to under worlds) - an underground bunker that was used during WWII and the Cold War.
The entrance to the underground bunker was actually through a metro stop. The young guy in the red sweater and yellow vest, in the picture above, was our tour guide.
It was really interesting... and creepy. A weird feeling that I can't fully describe but was something like cold, dark, and creepy stayed with me all week in this city. Berlin is amazing... and the way in which the city has embraced its history... and now advertises its history in a way, is incredible. I'm really glad I was able to experience this week.