What city should I chose of four?

Portugal, Lisbon and Porto. You may lose a little time traveling between the two, will you have a car?

Eileen ,based on your tastes ,Edinburgh would be it , hands down . As a second choice ,while Zurich is very nice ,and we enjoyed our time there , if I were choosing Switzerland , I would prefer Luzern . As well , not having visited Spain or Ireland , Ican't make an intelligent comment , and other posters who are better informed will be able to broaden your choice .

Regarding Portugal: I won't have a car, and planned to base out of Lisbon. I thought it would be possible to train or take a tour to Porto from Lisbon?
My understanding is that Porto is a very historical city.....is it feasible to see in one day? With regard to Edinburgh....what other cities would you recommend seeing, using Edinburgh as a base and traveling by train or tour outside?

Eileen ,Glasgow , about 40 minutes away by train is fascinating . A big draw there for us was the ability to see the work of the turn of the century art nouveau architect and designer Charles Rennie Mackintosh and that of his wife , Margaret McDonald .Mackintosh once remarked that while he had talent , Margaret possessed genius . It's true ! The Glasgow School of Art , The Willow Tea Rooms , Scotland Street School , House for an Art Lover ( in Bellahouston Park , just on the edge of town ) to name a few . For history and the role of Glasgow in nineteenth century industrialization , visit the People's Palace Museum .Another easy and lovely rail trip from Edinburgh would be Stirling Castle to the northwest . The castle is fascinating with a great deal to see . and the town is delightful . As well , don't give short schrift to Edinburgh . The medieval old town contrasts nicely with the eighteenth century Georgian New Town and the whole city is charming.

Thank you! I'm leaning more toward Scotland for the historical pull. In reading about Switzerland, although beautiful scenery, I'm not sure it would give us the historical city feel. Still also considering Lisbon
No one said anything about Ireland, so not sure if that would not be recommended? I did visit it 10 years ago (Dublin and middle of country, horse breeding farms) and found it all very interesting, but didn't get down to the southern part.

Throwout Switzerland (Zurich and surrounding).
You cannot go wrong on any of the others. They're all fine for your interests.

Of the group, and given your preferences as you describe them, I'd pick Edinburgh of the four.

Ireland would be more difficult without a car if you are wanting to spend time outside of Dublin.

Another vote for Edinburgh-wonderful city!

Eileen ,and anyone else who might be considering Glasgow ; On YOUTUBE if you punch up : " Charles Rennie Mackintosh Documentary " A Modern Man " you wil find a 45 minute narrative on the life and work of the early 20th century architect and designer ,as well as his brilliant wife , Margaret MacDonald . This documentary ,as best as I recall , coincided with a major retrospective of their work at the Metropolitan Museum of Art , here in NYC in the nineties . Seeing these buildings in Glasgow was a real treat for us , being lovers of Mackintosh and MacDonald's work . In any case you will be greatly informed and entertained by this wonderful narrative , beautifully presented by the British actress Juliet Stephenson .