Cobblestone streets or smooth sidewalks

I am sorry but there is simply no way to answer that question. What area in Spain? Similar to ask what area in CA would have smooth surfaces. You will encounter brick streets, cobble stones, and especially broken concrete and uneven sidewalks -- almost everywhere -- especially sidewalks. Repair of public right-a-ways especially sidewalks has never appear to have the highest priority.

One of the larger cities like Madrid or Barcelona.

Only small parts of Madrid are cobbled I think by the Royal Palace. Barcelona is not cobbled.

You can use the 'Street View' feature of Google Maps to walk the area around a hotel you are considering to estimate the quality of the walking surface.

I’m sorry, I meant Barcelona

@Yvonne... smooth surfaces. From the thousands of boulevards, streets, and passages in Barcelona, I can only recall three small ones left in the whole city which are still cobbled.

You would only really run the risk of cobblestone in the medieval villages north of Barcelona, like Besalú or Pals, and even then the majority of the streets will still be smooth.

Yvonne, does your husband use a cane? I'm curious because I am in a similar situation.

I don't remember any streets in Barcelona other than maybe a few in Barrio Gotic that are cobblestone. Most of the city has concrete sidewalks like any other 1st world city.