In 1969, Chattanooga's industrial smelters belched so much smog the city was ranked as having the country's worst air pollution. Forty years later, the smoke has cleared to reveal world-class climbing, Class IV kayaking, and nearly 100 miles of mountain-bike trails – all within 30 minutes of downtown. Treat it like a hub: Over a weekend, you can climb Sunset Rock, paddle the Ocoee River's middle-section rapids, and bike the new 10-mile section of Stringer's Ridge (located entirely within city limits). Cap it off with pints at downtown's Boathouse raw bar – reachable along the river by standup paddleboard.

More Information: Outdoor Chattanooga offers maps and rental information.