Wow, what a question! Lots of votes for Venice, and it is of course unique (other places have canals - even Birmingham! - but nothing like that) however it has a distinct aroma in the summer months, and at times in the rest of the year, so factor that in?!
Obvious places like Paris Rome & Madrid will get votes, but all the Scandi capitals are great, and Bergen too.
I'd suggest a few smaller places, Salzburg is exceptionally pretty, Cordoba is great too (& with that pretty much unique 'Mezquita') and Oporto is a lovely city, and if you like Port (!!) then a great many samples to be had touring all the firms based there!
I see some nominations for Budapest, it's very grand by the river, but a lot of the rest is pretty shabby, and they have retained some of the bullet holes the lovely Russians left for them?!
