Most German cities however established "Sperrbezirke" (off-limits zones) and charge the street prostitutes an amusement tax, that in the city of Bonn for instance is paid by the streethookers at parking meters, 6€ for a period of about 8 hours at nightime.
If you prefer to date a lady in your hotel, you can call some private escort girls in Frankfurt.
The Red-light district area in Frankfurt is known as Bahnhofsviertel, the block directly opposite main railway station (Hauptbahnhof).
It is one of the largest Red-light districts in the whole world, and literally this place is huge and full of sexy whores.
When you negotiate the price make sure: You will avoid to get scammed if you make things clear from the beginning.
Some hookers (usually the German whores that believe they are something better than their Latina and eastern European counterparts) promise you everything. If you do, this may happen: Suddenly she will only allow you to lower your jeans a little and will start to give you a hand job.