Last Monday was a holiday here in Germany and I used the day (and the 9€ ticket to take the train to Erbach and Michelstadt in the Odenwald mountains about 55 km south of Frankfurt, near the state border to Bavaria and Baden-Würtemberg.
This building is the district administration with the district concil of the Odenwald county: Erbach is the administration seat, the district capital, if you will, of the Odenwald county. Thats why all vehicles registerd here have ERB on their registration plates.