Our Trail of the Week feature is made possible through a partnership with Trail Run Project.
This route lets you see almost everything that Boulder, Colo., has to offer for mountain running by traversing five of the tallest mountains in Boulder: South Boulder Peak (8,549 feet), Bear Peak (8,459 feet), Green Mountain (8,150 feet), Flagstaff Mountain (6,983 feet), and Mt. Sanitas (6,843 feet). Any one of those mountains can make for a great run, but combining all five in one loop can be downright epic.
There is a reason this is a frequent test piece for both pro and amateur ultrarunners. No matter how you combine the mountains—a variety of trailheads and interconnecting trails make numerous options possible—the Skyline Traverse is a long, arduous ultra-style run that has a variety of technical terrain and steep trails with a lot of gain and descent in relatively short distances. But it’s a great challenge with great views throughout—a perfect way to explore all that Boulder has to offer.
The most significant creek crossing in the first half of the route is at Bear Canyon, after descending from Bear Peak just before you head up Green Mountain. This is one of only a few places to fill up water mid-journey, if you need to. There is also a water fountain at the Chautauqua ranger station, and the ranger station atop Flagstaff Mountain usually has bottled water for hikers (because the fountain has been out of service in recent years.) The next (and last) place to get reliable water is the drinking fountain at Eben G. Fine Park.
Miles: 16.1 (But it can be as long as 20-22 miles, depending on the trailhead and route you select)
Runnable: 71 percent
Average Grade: 13 percent
Max Grade: 63 percent
Total Ascent: 5,273 feet
Total Descent: -5,348 feet
Highest Elevation: 8,549 feet
For a closer look, check out the interactive map, data, photos and virtual run simulator courtesy of Trail Run Project: