There’s many lists, so it vastly depends on who you ask, or rather on what you consider your priorities. What do you consider a “city”, for example? Most of the 100 or so Italian provincial capitals are about 50 to 100 thousand people each, is this your target?
Many foreigners when speaking of Italy automatically assume a seaside position, but that’s not a given. Or a historical place, which is often the case but not always — Latina, for example, was founded in 1932.
Also, I assume you want to live here as a pensioner? It’s a good idea if you have a bit of money saved and you can spend at least, say, one thousand euros per month per person: there’s lots of cozy and astounding places in the center and south of the country, like Potenza or Ancona or Bari, which are tied for the lowest prices.
A view over the rooftops of Potenza, 65 thousand inhabitants, regional capital of Basilicata.
Seaside view of Bari, 320 thousand people, proud capital city of the Apulia. The inhabitants are fond of saying that if Paris had a seaside it might be called a less glamorous version of Bari.
But if you are looking for a job the equation changes drastically, as you’d have much better chances in the north: look into Bologna, which is not es expensive as the cities in Lombardy, Veneto or Piedmont but just as rich.
If you have money to sink into buying a flat or house, Molise or Calabria are the best bets for real estate bargains, especially if you can be convinced to like a somewhat bucolic lifestyle. If you are looking to rebuild a house from the foundations up, there’s a few small towns which will sell you one of those for a symbolic price, as long as you promise to invest in renovation and live there. Go browse the municipal websites for Ollolai (Nuoro) or Nulvi (Sassari) if you are intrigued by Sardinia; or Montieri (Grosseto) if you are dreaming of Tuscany. But in all such cases you are resigning yourself to live in a village, not a city, and the closest city will likely be one hour by car.