If I had to live in a city it would be in one not too big and not too small, with plenty of history, culture and nightlife, but easy to get out of into great countryside. Glasgow and Newcastle in the UK, Bordeaux or Marseilles in France, Berlin's a great place too. Madrid or Seville in Spain, Izmir in Turkey, Copenhagen or Stockholm. I like Chiang Mai in Thailand and Melbourne in Oz. I think I could probably live in any of those cities. My experience of the US is small, but I found DC a very manageable size. Huge metropoli are insufferable. Paris, London, NYC, LA, Bangkok, Istanbul are all just too exhausting for anyone over the age of 40.