oh besides the FKK clubs in Frankfurt there is the underated Red Light District right across from the Central Train Station not hard to miss, beware of the strip clubs even though i didnt go in there they try to bust some hardball tactics to get you in there so that means its a ripoff this was confirmed by a friend of mine who was stationed out there and one i met on the trip, basically what there RLD consist of is 7 or more story buildings all flashing red lights at night and you just walk through and if you like then nothing more needs to be said going price was 30-50 euro, quality ranged from disgusting to goddamm you fine and everything in between, some of these places was pumpin the heat like it was out of style though, but theres over 7-8 of these buildings, me personally i didnt do anything there but did walk around for quite some time. peace