We are planning on sending our parents on a citytrip for our dad's 60th birthday. Both my parents are very interested in architecture and enjoy visiting "architecturally beautiful" cities.
They've already visited Paris, London, Prague and most of Italy. We were considering offering them a trip to Vienna or Budapest. Which of the two cities is the most beautiful? The most pleasant? The one that has the most to offer? The most entertaining? Where should we send our parents to?