A UK city that when you visited you thought, "oh, it's actually pretty decent here".
I'll start. Norwich. I had little to no opinion of it other than Partridge's annoyance at the pedestrianisation of its city centre (traders need access to Diiiixxons!). Then a mate from there took a few of us to stay at his family home for a weekend. Turns out it's really nice. Plenty going on. Lots of nice places to eat and drink. Culture, events, etc. A cathedral, and some nice built environment. I don't know why but it kinda surprised me.
Now, wherever Norwich comes up in convo (it's rare I admit) I chime in with, "it's actually pretty decent y'know".
What are yours? Towns are allowed as well, and none that are already widely considered to be nice cities.