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The course of the eponymous underground, unsanctioned, unofficial, mountain bike race/adventure.

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10,589' 3,228 m


5,588' 1,703 m


8,965' 2,733 m


11,815' 3,601 m



Avg Grade (3°)


Max Grade (19°)

This has been hidden from our maps to prevent overlap with existing trails, or because our research has found there is no legal access.

Dogs Unknown

E-Bikes Unknown


An amazing adventure taking you from the mountains to plains on some of Boulder County's best and most obscure mountain bike byways.

Note: This is a giant ride, and has gotten a bit of a cult following. Check out the dedicated website for more information:

Need to Know

Start this ride by taking the RTD Nederland(N) bus route from Boulder to the Nederland High School. Alternatively, set up a shuttle by parking at the Nederland High School or at the bus stop in Nederland.


From the Cougar Slayer website, "From Ned high school, ride to the town of Eldora. Start up Caribou Flats (CR505,128J) toward the top. When near the top and the trail flattens out a bit, turn right and descend singletrack to the little village of Caribou.

Once in Caribou, climb Caribou Road briefly and descend Sherwood Forest. Youll pop out close to Mud Lake, get on the dirt rd to the Peak to Peak highway. After passing Sugarloaf Road on the right take your next left on the frontage road entrance (CR103). Stay on this until it ends back at the Peak to Peak highway, dont get off early.

Ride down Peak to Peak to the Colorado Research Center Road entrance, Sourdough Trail. Ride the full Sourdough Trail (Sourdough Trail - Southern Half, North Sourdough) to the Brainard Lake parking lot. Ride the South Saint Vrain Trail to the Peak to Peak highway. Turn right (south) on the Peak to Peak, take the first left on the CR103 then hang a slight right which becomes 100 to Gold Hill Rd.

Take a right on 372 which goes around Gold Lake and merges with 509. Continue on the main dirt rd, taking a hard left on to Strava segment hooter. Hooter Ts at the end, take a right and follow the dirt Rd to the next T. take a left followed by an immediate right.

Follow it up to the top. Hit a rocky and fun descent to the top of Slaughter House Gulch and Flying Squirrel. Drop down directly south on Flying Squirrel / county rd 509 then up Lefthand Canyon to Lick Skillet Road. Ride Up Lick Skillet Road to Gold Hill.

Continue West through Gold Hill. Descend Todds Gulch at the intersection of Gold Hill Road and Switzerland Trail. Go right on Switzerland Trail to the Sugarloaf parking lot. From the parking lot take the Switzerland trail west to dirt rd 233C. 233C merges with Gordons Gulch right were it becomes fun.

After the descent continue on Primos Road to Sugarloaf paved road. From Sugarloaf take a left on Labelle dirt road. Descend Arkansas Mountain to the Sugarloaf paved road. Left to Betasso, down Link trail. Ride down Colorado 119 (Canyon) to the Boulder Creek Path(entrance at large gravel turnout on right). Finish up on the Boulder Creek Path to Eben G. Fine gazebo."

History & Background

The Cougar Slayer "race" has been run since 2012 as a self timed Strava event. Participants can choose to ride the course at the time of their choosing or on a designated race day in August.


Shared By:

Jim Mapes

Trail Ratings

  4.4 from 10 votes


  4.4 from 10 votes
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in Colorado


9 Views Last Month
17,764 Since Jul 28, 2014
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"Look out" for awesome fall colors on this trail.
Oct 5, 2016 near Nederland, CO
Parts of the trail are just as they always were.
Jun 26, 2013 near Nederland, CO
A nice little pause in passing Brainard Lake while connecting Little Raven Trail to South St. Vrain Trail.
Jul 23, 2019 near Nederland, CO
This section has a lot of moderate technical downhill flows.
Dec 26, 2020 near Nederland, CO
This picture was taken towards the beginning of the trail towards the Magic Bus trailhead. I believe this picture was taken in June 2018/2019.
Mar 6, 2022 near Nederland, CO
Desending the Lookout trail.
Jul 4, 2017 near Nederland, CO



Current Trail Conditions

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