End of July, 4 days, no children, warm but not hot!

[bottersnikes]

Dh and I will have 4 days to ourselves at the end of July (woohoo!) and would like to take the opportunity to go abroad and see somewhere new.
We love culture, art, architecture etc and would prefer a city, but not too busy or too hot. Amazing scenery would be a bonus!
Does anyone have suggestions for somewhere that might suit, probably northern Europe (due to the heat)? Ideally it would be somewhere that neither of us have visited before, so NOT France, Germany or Sweden.

Bilbao?

Iceland
Edinburgh
Copenhagen
Amsterdam
Bruges

Gdansk in Poland is supposed to be lovely. Google images certainly backs that up.

Tallinn? The old town is lovely, tons of history, and it's likely to be warm, but not hot. Plenty of nice restaurants. Also has beaches.

Suggestions already, thank you!
I hadn't thought of Edinburgh, that could be lovely. Dh has been, but only to the Tattoo, so he might consider it.
What is there to see in Copenhagen, apart from the very tiny mermaid?
Bruges would be good, as we could go by Eurostar rather than flying. Is there enough to do/see to fill 4/5 days?