Hike, bike, or snowshoe this 3.1-mile loop to pioneer ruins and a relaxing waterfall in Patapsco State Park, a short drive from downtown.

Hike or ride smooth singletrack on this 7.2-mile lasso-loop, which climbs gently through rich scrubland and ponderosa forest to a killer mountainside overlook.

Cruise 5.2 miles along gentle foothills, Ireland-esque pastures, and past an old sawmill to a vista overlooking Boulder Canyon and the Front Range.

This beautiful 4.3-mile loop adjacent to the Illinois River adds welcome relief--waterfalls, sculpted sandstone canyons, and impressive overlooks--to the usually pancake-flat landscape.

Bag two peaks on this 9-mile, fido-friendly loop around Boulder's signature Flatirons.

Ascend North America's tallest dunes for a day surrounded by alpine peaks, a desert valley, and shifting mountains of sand on this 6.6-mile loop in America's newest national park.

Only 8 miles from downtown, this diverse 3.4-mile loop curves gently around a pair of crystal-clear lakes (bring binocs to watch waterfowl) to an old trading post.

Named after a Forest Service employee who disappeared while hiking in the late 1990s, this 6.5-mile loop links rugged high desert terrain with deep, cool forest.

Thanks to only a little elevation gain, this 7-mile loop offers flatlanders great rewards (big views, wildlife, solitude) without much suffering. Pack plenty of water and sunscreen.

This 5-mile loop wanders through huge redwood stands along the western slope of the Santa Cruz Mountains. Extend the trip with an overnight at a Sierra Club hut.