Language learning fail ;)
Well, I can't say that I understand people's searching habits, even if I happen to work for a company with a popular search engine... I do understand the German Sauna searches, however. German saunas are among my favorite places on the planet, but I enjoy reading reports by people from English-speaking countries who experience them for the first time. (I haven't decided whether people from the US or the UK have a more difficult time getting their heads around the concept.) The place you talk about in Berlin sounds cool, and I may consider going there when I'm in Germany in September, but if you ever find yourself in Munich, you should check out Therme Erding.
No idea about people from U.K., but, yup, the sauna is sort of like the idea of soccer in the U.S., before the women started winning, or real coffee before Starbucks popularized / bastardized the idea, and beer, in the bad old days when it was pretty much just bud. (Imagine my astonishment finding out most U.S. beers are made out of corn - is that right? We are under some mass hypnosis, thinking this was great stuff, or we put up with it purely to get drunk.) Anyway, so saunas aren't hugely popular or understood well, people mostly head to the whirlpool, the sauna is that empty room with the electric heater usually avoided. HOWEVER in the far northern reaches of Minnesota and Wisconsin, perhaps because of Finnish immigrants, you can still find some real, saunas, heated with wood, and close to a lake - nothing better than jumping into a hole in a frozen lake. Yes - the freezing water is the most important part of the sauna ritual. In YouTube, search for "maplelag plunge" for one excellent example.. To give another idea of the American viewpoint of a sauna, check out Conan O'Brien's visit to a Korean sauna (youtube again, if avail over there.)