It's the former "Hotel Cristall", still being renovated. The area isn't great either (but better than Premier Inn Mediapark). If you just want something cheap and very near the Central station, I'd probably go for the IBIS inside the station itself.

Note that the location of the Premier Inn on Google Maps is incorrect. The hotel is on the other side of the street (if you go to street view, you can still see the outline of "hotel cristall" on the top floor at the corner of Ursulaplatz and Ursulastrasse).