It’s hard to pinpoint what qualities 20-somethings go for in picking the perfect city. Sustainability, efficient transit systems, cleanliness, and affordability may make the top of the list. Dig a bit further, and others may add walkability of streets, prevalence of gyms, and overall well-being. Number of happy hours, zoos, and places to booze may be factors, too. So running with that list (plus a few city-specific features we just couldn’t resist considering) we bring you 20 of the best cities to enjoy your carefree twenties (or thirties).