Denver, Colorado is one of the most active cities in the United States. The bike-friendly city offers 850 miles of trails to cyclists, in addition to 100 free public tennis courts and 200 parks. Like Seattle, Denver is home to one of REI’s two flagship stores, so anyone who forgets their hiking gear or bicycle helmet can easily rent or buy replacements.
Opportunities to be active don't stop at the city limits. The Rocky Mountains are right in Denver’s backyard and offer such pursuits as skiing and hiking, and it's close enough that you can spend all day on the mountain and still get home in time for American Idol.