Boulder is the home rule municipality that is the county seat and the most populous municipality of Boulder County, and the 11th most populous municipality in the U.S. state of Colorado. Boulder is famous for its colorful Western history, being a choice destination for hippies in the late 1960s, and as home of the main campus of the University of Colorado, the state's largest university. Furthermore, the city of Boulder frequently acquires top rankings in health, well-being, quality of life, education and art. Boulder has a dry climate typical for much of the state and receives many sunny or mostly sunny days each year. Winter conditions range from generally mild to the occasional bitterly cold, summers are very warm and dry. Boulder is surrounded by thousands of acres of recreational open space, conservation easements, and nature preserves.