We spend Boxing Day in Mainz, the largest city in the Rhineland-Palatinate region of Germany. The town boasts numerous monuments and the Gutenberg Museum which, with its collection of the history of printing, books and writing, is one of the best-kept secrets. During a guided sightseeing walk, we admire the sights of the city, before the captain invites us to a festive Gala Dinner on board. We then cruise to Cologne overnight.