I loved Amsterdam, too. We stayed in the Jordaan in a typical Dutch canal house as my future DIL was working there. I only lived in fear of stepping outside the door and being run over by a thousand bicycles!
Rome + Amalfi Coast, Athens, Madrid, Valencia (Barcelona was OK), Paris, Edinburgh, London, Stavanger in Norway, Berlin (before unification was fascinating, both sides), Munich, Zurich and...
I absolutely loved Vienna and visited in the 1980s when still single. I went to the Stadtpark and they had a Strauss-like orchestra playing waltzes in the bandstand. I was seated next to some young men at the terrace cafe, and was asked to dance many times. Thank goodness for childhood ballroom lessons in the 1960s!
www.wien.gv.at/english/environment/parks/stadtpark.html
Also the Schoenbrunn Palace (very much like Blenheim), outside of city, was great. The Hapsburg one in the centre was good but not as grand. Oh, and the pastries, konditorei, sacher torte. Yum! Then I went on to Salzburg, more touristy but still nice with dramatic scenery.
Back in the US, Boston is my favourite big city, but am very partial to the Maine coast.