What's more likely to be nuked, London or Tirana?
Only 7 "urban areas" have more than 1 M inhabitants. Of those, the first two have almost 25% of the country's total population [0].
Also, I'd expect the huge and sparsely populated Nordic countries to fit the bill, too.
[0] https://fr.wikipedia.org/wiki/Liste_des_aires_urbaines_de_Fr...
But frankly, I don't believe a nuclear war is imminent. In spite of what we see in the new, Putin's army is moving on steadily and occupying more and more areas he wanted to have. At some point Ukraine will lose access to the sea. Then Putin can say, OK, I agree to peace - but he will never give the occupied areas back. And good luck getting these cities back without killing your own people - this is a completely different situation than defending a city that hasn't been captured yet.
Nuclear war would be possible if NATO decided to intervene. But they are crystal clear they will not and nukes are the only reason. Everybody is sending a lot of help, but not a single soldier (even though some individuals want to go on their own - but that's a completely different story than a military intervention).