Delta has a decent sale for travel between Detroit and Munich over the Christmas period both for non-stop travel and via Atlanta. These fares can be booked with Virgin Atlantic codes that increase significantly the earnings in terms of MQDs and RDMs.
Christmastime in Austria and Germany is a magical time of the year with plenty of markets across the country with modern versions such as Tollwood in Munich (Review here) or Salzburg and the town where Silent Night was first sung 200 years ago... In Munich you can also explore the Munich Airport Visitors Park while in Bavaria you can find Schloss Linderhof , Oberammergau and Schloss Neuschwanstein (Sleeping Beauty Castle)
DTW-MUC would earn 16173 MQMs 4313 MQDs 1.977 MQD Ratio
Delta Diamond members would obtain 47441 RDMs, Platinum 38815 RDMs, Gold 34502 RDMs, Silver 30189 RDMs, Base 21564 RDMs