I loved walking all over Madrid and exploring small streets, museums and wonderful restaurants with fabulous food. Prague is also one of my favorite cities. Barcelona, not so much. I am planning to go to in early June to northern Italy/Florence or Greece, doing Athens and an island or two (not Mykonos or Santorini). Thanks for your thoughts and recommendations.
I'd pick Florence over Athens, if you have to choose one. IMHO, there is more to do and see in Florence, but I've been to both and I like both cities. Not sure why you didn't like Barcelona, but Athens is big and is similar to Barcelona in city attributes.
Prague and Florence are two of my favorite cities. I, too, am not a fan of Barcelona. But everyone has his own preferences.
I've never been to Athens, but for whatever reason I'm not particularly eager to visit Greece in general. Don't care for Greek food, which may have something to do with it.
Been to all of those cities and loved them all. Madrid would be my least favorite of those four cities.
Florence is special with the Renaissance history, art and architecture. Athens has the incomparable Acropolis with the Parthenon as well as some great museums like the New Acropolis Museum and Museum of Archaeology.
Save Athens for a trip to Greece and see some of the islands on a cruise.