My husband and I also took a Danube cruise recently. We were on Viking Cruise lines, starting in Budapest, then traveled through Austria and Germany, ending in Nuremberg. We were in Budapest for three days before the cruise, and barely had enough time to see what we wanted.
One thing that impressed me about the whole tour was the layers of history, and how they are periodically almost (but not quite fully) scraped clean for the next layer. The medieval layer was there in a few imposing buildings, or the vaults below our hotel in Buda. There was some Renaissance stuff as well, but most of the historical things dated from the Baroque era. They had pretty much cleared everything to make way for the exuberant architecture and decoration of that era.
I’ve been to England several times, and there the medieval and renaissance layers are more prominant, with much less Baroque.
When we got to Nuremberg, there were photos of the city right after WWII — almost entirely leveled, then rebuilt to keep much of its historical character.