I am going to Frankfurt and the Cologne. What are the ages of girls and guys.  At 57 would I feel uncomfortable?

I don't think so.  I've seen a lot older than that.  It seems to be a broad ranges of ages.

youll fit right in

I am a few years older than you, have visited Oase twice, Golden Time once, YingYang (in NL) once. Never a problem with my age. Of course, YMMV, and the girls do have their preferences as do we. But, with the numbers of girls, even geezers like us have plenty of choices. The ages of girls/women range from 18 to 40, with most in their early 20's. Or maybe those are the only ones I noticed. Go an enjoy yourself, but don't take the first girl who approaches. Relax, look around, get the feel of the place. Or visa versa!

ditto that...I saw all ages there...and I'm in my mid-40's..so I didn't feel odd...you'll fit right in.