Was asked email to check in online and that's what I did and paid for. Then in the hotel at the reception came a message that I had not checked in. The staff present gave the impression that I had made a mistake because I checked in online.
During the check in process, the nightly rate was then charged to my credit card again. When asked what this is about, I was told with a shrug, this is due to the online check in. It was promised that it would be sorted out. What happened was Nix.
The next morning I asked again at the reception what the situation was. Again, the receptionist gave the impression that the mistake was mine.
Very unsatisfactory experience that spoiled my weekend in Cologne.