In Erfurt, I highly recommend the recently-built Grand Hotel am Dom (an Accor property). It is just around the corner from the Dom and is right across the street from the Theater Erfurt, the new opera house that opened in 2003. It is very easy to reach if you are arriving by train - from the outside of the Hauptbahnhof, take EVAG streetcar #4 to the "Theater" stop - it takes just a couple of minutes from Anger Square (the shopping and transportation hub). The rooms are modern and well-equipped, with beautiful public areas and a very good restaurant serving a truly outstanding breakfast:

http://www.grand-hotel-erfurt.de