What cities have smooth streets

Reykjavik, Iceland has nice easy sidewalks and a walking path down along the harbor and the water. Salzburg and Munich have smooth sidewalks, but not everywhere, so you would just need to pay attention a little bit.

Most of the cities of Spain have smooth surfaces.

I seem to run into non-smooth sidewalks often, especially in the historic sections of cities. There are also places where the sidewalks are broken up, sloping, or too narrow for two people to pass, so someone has to step down into the street, which may have uneven paving stones or cobbles.

On my current trip, which covered Estonia, Latvia, Lithuania and two cities in Turkey (plus other, less problematic destinations) I found myself covering a lot less ground than usual because I had to be so careful not to fall.

Excellent question. I think if you avoid ' Gamla Stan', Old Town in Stockholm, you should have smooth walking surfaces. If you're staying anywhere that has a host, you could certainly look at a city map with the front desk & ask for some guidance. In Stockholm, I seem to recall almost all the streets are not only are smooth, but many of them have designated pedestrian walkways, especially along the waterways. Then you could come to Uppsala, there are only a few cobblestone streets, which would be obvious & avoid walking uphill to the Cathedral. Rome isn't a good idea, lots of uneven surfaces. Good luck! (PS, Thinking more about it, have you considered walking sticks? You can get the periscope kind that will fold up inside your checked suitcase, can't carry on due to the points they have. Many Europeans use these daily for walking, no one will think anything of it. Or buy when you arrive. AND well done that you still want to travel!!!)

unfortunately the UK - England in my experience but I expect the same in the other 3 nations - uses special raised dots in pavement at crossing points and cut kerbs so that blind and vision impaired people can find the safe place to cross by feel underfoot.

I expect that that would be a problem for you but you have said that you have no problem with London, so I don't know. I know that my wife needs the tactile paving.

Think about Berlin. It's base is flat (fast marathon times) and the walkways in center areas are often optimized for people with handicaps - less in outskirts. The walkways have often a side of small copple stones and a center area made of stony slabs.

Barcelona and Madrid have smooth sidewalks and walkways.

Vienna and Berlin.