Great stay in the calm room of Regina, all was made to have a nice stay. We slept very well. The flat is well located between Hauptbahnhof and Nordbahnhof next to Naturkunde Museum. All accomodations were closed to the flat, we enjoyed our stay.
The flat is very clean and sharing bathroom and kitchen was not a problem, Regina is a good host very respectful.
I highly recommend Regina and her flat if you need a calm place in Berlin.