From prioritizing green spaces to encouraging the use of electric vehicles and alternate fuel sources, The Mile High City does its part for the planet. Denver is the only U.S. city included on National Geographic’s list of “Eight Sustainable Destinations for 2021 and beyond,” thanks to the city’s goal of achieving 100 percent renewable electricity by 2023, and 125 miles of new bike lanes and solar gardens planned throughout the city. Denver also ranked as the eighth “most sustainable” city nationwide in 2021, according to Rocket Homes.