Exchange Student Weekend Travel - In need of suggestions for Autumn destinations

I’ll be doing a study abroad university exchange from the U.S. to the UK this Autumn. I want to do a few weekend trips to other countries while I’m there. I have a list of potential weekend destinations, but I would like any suggestions on which spots will be best for October/November so that I can pick between them. I’m interested in museums, architecture, and nature, and I’m not really into nightlife. I prefer to just chill, walk around, and immerse myself in new cities. My options are listed below; trying to stick to cities that are located right near an airport, since I only have weekends open. Thanks guys! (for reference, I’ve already been to Amsterdam, and I plan on visiting Italy, Slovenia, Austria, Germany, Switzerland, and France all in the weeks before my school term starts, so they are all off the list). And yes, I am aware that this is a lot haha, but I’m experienced with a jam packed travel schedule.

- Prague

- Budapest

- Copenhagen

- Spain (Madrid, Barcelona, Seville, or any other cities with an airport)

- Portugal (Lisbon or Porto)

- Athens

- Brussels

- Croatia (Dubrovnik or Split)

- Krakow

- Sweden (Gothenburg or Stockholm)