Eldorado Canyon State Park
Eldorado Springs
Rock climbers frequently take advantage of the walls of Eldorado Canyon, but hikers enjoy this spot, too. The park near Boulder can be at capacity in the summer, but in the fall you're virtually guaranteed entry on an abundance of trails, from quad-busters to easy strolls. When snow falls, this is also a popular spot for snowshoeing and cross-country skiing.

Bear Peak Trail
Boulder
Boulder's overtaxed trail systems lighten up in the autumn, but they can still be social hubs. For those seeking greater solitude, a trek up the Bear Peak Trail is in order. You'll experience a respectable 3,018 feet of elevation gain over 7.7 miles as you make your way up this magnificent Front Range peak.

Waterton Canyon
Denver
Head to Waterton Canyon and walk the first segment of the Colorado Trail, a roughly twelve mile out-and-back hike along the South Platte River. The trek is on gravel roads, which you will share with bikers and horse riders; along the way, you might catch a glimpse of bighorn sheep. Dogs are not allowed on this part of the Colorado Trail.
 

Green Mountain
Lakewood
William Frederick Hayden Park is located on Green Mountain, a wide-open mesa sandwiched between the high plains and the Front Range. If you're looking for epic views without going above treeline and don't mind the sun blazing down on your head, these trails — including a 20.8-mile loop with 3,566 feet of elevation gain — could be just the thing you're craving.

Mount Morrison
Morrison
Located near Red Rocks Amphitheatre, Mount Morrison offers a 3.5-mile hike with 2,113 feet of elevation gain, expansive views of Denver and the plains, steep singletrack and a few opportunities to scramble up rocks.

Meyer's Homestead Trail
The 5.4-mile Meyer's Homestead Trail just outside Boulder, in the Walker Ranch Open Space, offers visitors a quick jaunt past the ruins of historic buildings, next to a winding creek, through the site of a forest fire, and up a mountain to some stunning views of the Rockies. The trail is a calm oasis outside Boulder, and well worth a visit.

Chautauqua Park
Boulder
Few Front Range trailheads boast the number of beautiful hikes – and aggravating hikers – as Boulder's Chautauqua Park. During summer months, the parking lot is guaranteed to be packed with all manner of trail runners and hikers sporting high-end gear. Look up the trails leading into the woods and the human beings appear a lot like ants. Come fall, this trail system is still well-used, but you're likely to find a parking spot and a little alone time if you trek in far enough. Here you can hike any of the popular Mesa, Royal Arch or Baseline trails along with routes to the first, second and third Flatirons.