It doesn't seem that anyone has mentioned Brugge, on the Belgian coast, not far from either Brussels or Amsterdam, or the ferries to the UK....it's not that any one thing is so remarkable (except a Michelangelo 'Pieta" that's NOT behind glass, it's that the whole is a small gem, built on canals...for me one of the most memorable towns in Europe. Also, for either Eurrail or Britrail passes, which may be useful if not drivng (I certainly agree that medieval or older cities are not designed for cars) they must be purchased before you leave N.America...