Just West of Denver, Arapaho National Forest is where the locals go when they're tired of the crowds. The National Forest's borders encompass the Indian Peaks Wilderness, home to world-class climbing, multi-day backpacking loops, and enough snow melt-fed alpine pools to put Minnesota's "Land of a Thousand Lakes" moniker to shame. The other prominent wilderness area (there are six total within the national forest) is Mt. Evans, a popular Fourteener just outside of Idaho Springs, which happens to be home to Westbound and Down Brewing, the best spot along I-70 for a post-summit beer. Don't want to share the vert? Head to the Never Summers, a range of 12,000-footers threaded together by single track trails and long-range views.
There are a number of different entry points into Arapahoe National Forest.
To access the Indian Peaks: From Denver, take Hwy 36 to Boulder, then up 119 to Nederland and the Brainard Lake area, a popular launching pad for hikes as well as backcountry skiing and snowshoeing in the winter.
For Mt. Evans: Head west up I-70 to access the wilderness area; follow signs off the highway to the eponymous Fourteener's trailhead, and use Gaia GPS to pick your hike.
For the Vasquez and James Peak Wildernesses: Take I-70 to I-40, north of Empire, CO, to access trailheads year-round. (Parking on Berthoud Pass offers an easy-to-find gateway for both skin laps as well as longer ski traverses.)
The Arapaho National Forest is most popular for hiking during the late summer (watch out for afternoon thunderstorms above treeline in early June through mid-August), but there's great tree skiing and backcountry skin tracks for a variety of experience levels throughout in the winter, as well.