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Four Mile Canyon, Switzerland Trail and Trails through Niwot and Gun Barrel

Boulder, Colorado , United States
58 mi




ft elev +


This ride is brought to you by Laura and Rose of 
Gravel Bike Adventures is a Colorado-based gravel biking website that believes it is vitally important to include women’s voices in the gravel biking industry. Our goal is to encourage people (especially women and members of the LGBTQ+ community) to explore the power of the outdoors through venturing onto dirt roads. Our interactive website provides routes, downloadable maps, advice and other resources. The tools on the website help to build community by giving cyclists the confidence to see what is possible, get inspired, spark conversation and ultimately plan their own adventures.

Miles: 58
Elevation gain: 5,700 ft
Gravel ratio: approximately 70% gravel / 30% pavement
Difficulty Rating: ⛰⛰⛰⛰⛰  (out of 5)
Enjoyability Rating: ⭐️⭐️⭐️⭐️⭐️ (out of 5)

Highs: This route highlights the typical joys of gravel riding in Boulder: limited cars, great views, tons of different surfaces, challenging climbs, and animal sightings.
The route starts off on quiet roads with steep ascents. Just as you get really tired, you get a looong descent down Left Hand Canyon.  The final part of of the ride is a lovely tour of Gun Barrel and Niwot on the Lobo gravel Trail.
We love Four Mile Canyon Road!  It is a great gravel road and has quaint areas along the way. The atmosphere of Four Mile Canyon feels like a funky and fabulous combination of Europe and the Wild West!
Switzerland Trail is a rugged forest/jeep road that connects Four Mile Canyon to Gold Hill and Left Hand Canyon. It is the most technically challenging part of this route and it felt good to conquer it with confidence.

Lows: Switzerland Trail is generally very quiet and all of the Jeeps we encountered were courteous when we passed. We did not find the same when it came to the ATVs and dirt bike drivers. They sped past at alarming speeds and threw a lot of dust in the air! 😕
Crossing Highway 36 is a bit sketchy. We had to wait quite a while to find a break in traffic in order to safely cross. (Please be careful!)

Do this ride if you want a long climb with mixed road surfaces and some technical challenges on rocky jeep trails. You’ll will earn the views at the top, and enjoy a smooth, fun and fast downhill on Left Hand Canyon, then wind down on the flat and fast dirt roads of Niwot and Gun Barrel.

Take Aways (what we learned): It has been fun to learn how to best do gravel biking adventures. We watch the weather apps, we plan our route, we have exit strategies in case we get tired or something happens to our bikes, we look at the elevation profile and when parts of our route include dotted lines instead of clear gravel or paved roads on, we do a little more research to understand what the terrain and technical biking may be.
When we are exploring new routes, the security of GPS is critical because it has the route pre-loaded and all we have to do is follow the dotted line. It allows us to relax, enjoy the ride and know that we can’t get (too) lost!

Other Notes:
The Switzerland Trail is pretty rocky and rugged! We most recently rode this route with 700x35cm Panaracer Gravelking SK+ Tires (set up tubeless and pumped to 40 psi) and had no problems but could have been a little more comfortable on a slightly wider tire.
After you depart the city of Boulder, there are a few places along the way to stop for bathrooms but be prepared to carry what you will need to keep you going in terms of water and food. (There are bathrooms at the Mount Sanitas Trailhead off of Sunshine Canyon and Buckingham Picnic Area off of Left Hand Canyon.)

Driving Directions to the Start: We parked near the The Sports Garage bike shop in Boulder where there is plenty of easy street parking. (We love the friendly folks at The Sport Garage, so don’t hesitate to stop in!)
Poorman Road View
In Four Mile Canyon
On the Switzerland Trail
On the Switzerland Trail
The views descending on Sawmill Road