I whole heartily agree about Sauna Thermas. I went 3 times within the last week and was thrilled by the number, variety and quality of the rentboys. I met guys from Spain, Egypt, Romania, Bulgaria, Panama and many from Brazil. The sauna is very clean and seems to be well managed. It doesn't have the same friendly vibe as Meio Mundo in Rio but it easily matches the quality and quantity of guys in Club 117. As with the saunas in Rio, it very definitely helps to know some Spanish (most of the Brasileiros speak Spanish as well as Porteguese).
As a side note, I totally fell in love with a stunning man from Brazil. Somehow, between my fumbling Spanish and his limited English, we were able to communicate and we spent some "quality time" together in my apartment (a couple of times). He returns to Rio in December and now I'm tempted to take another trip to Rio. Hopefully I'll come to senses when the infatuation wears off!
Also spent some time in Madrid and made the obligatory trip to Sauna Adan. All I can say about Adan is, ho-hum. If you're ever in Madrid and are interested in Saunas with rentboys, check it out -- but don't go out of your way. I do have to say that I LOVE the city of Madrid. As far as cities go, I'd take Madrid over Barcelona any day. In terms of rent boys, Barcelona is far superior.