Denver, oh Denver! Where to begin; 300 days of sunshine, 4 season in a day, legal marijuana, healthy and accepting culture, nature abound, high quality of living.
So many things in Denver and in fact Colorado draw people by the thousands. When I lived in Denver (2009-2010) it was the beginning of the boom and natives were already sick of the over population in their beloved city. See when mass amounts of people move it causes problems in housing, jobs, shopping, roads, air quality and nature. Housing especially has gone up significantly, my old apt cost $455/month with utilities just 1/2 mi from downtown. Now that same apt is in slight disarray and the rent has almost tripled to $1,100/month.
Denver maybe the largest city but by no means the only place to see. Aspen is renowned for it's winter skiing and lodges. Fort Collins is the northern sibling to Denver, quaint, quiet very picturesque Midwest town. Aurora is fast becoming a go to medical college town and it's Air Force base is a large employer. Boulder is the techie, hippie mecha for Colorado. Black Hawk is the mountain town where you can gamble in old miner's houses.
So progressive and yet so very traditional in other aspects. Denver is known the world over for the liberal views on many things but mostly it's views on pot and recent legalization. But the city is conservative too they have traditional jobs 9-5 banking, medical, business, consulting and college. I will say this city more than any other I have been to shows me what it's like when people are genuinely happy. They way you interact is different, your productivity is different even exercising and eating is different. I won't say Utopia, because it is not, but certainly something makes most people happy. Maybe it's the good job market with high salaries, or nice homes, or great neighborhoods with parks and activities, or outdoor living and sports or maybe it's just the 300 days of sunshine a year. Whatever it is I think you will find Denver to be a most hospitable and friendly place to visit or live.