In Koln itself you really only have Samya and to the north side Mondial. Both are considered to be amongst the top two "party clubs". They both only become interesting in the evening (or night even), with a lot of Romanian music and plenty girls dancing. I've been told quite a few a girls want to work there because of the atmosphere, even when they could make more elsewhere.

You sometimes need to be carefull with service, because stuff like DFK is not a given for every girl... seeing how you liked Mainhattan though, in comparison it is about the same. Mondial is more focussed on a Turkish clientel, which means girls are more attuned to quick sessions without DFK.

In the vicinity of cologne you have clubs like Babylon, Eden and Parksauna residenz. All of which have their strengths, but fewer girls than in Samya and Mondial. Even with the sketchy service sometimes, Samya is one of my favorite clubs: i always have a blast...  last week I left at about 5.10 am.