The Boulder Skyline Traverse Trail is TOUGH but sooo worth it! This trail summits the five highest peaks in Boulder (listed below) and is just over 16 miles one way with about 6,000 feet of elevation gain. This one had been on my to-do list for awhile, but I pretty much made up every reason under the sun to avoid it- work, travels, life etc knowing how tough it would be. Then March of 2020 rolled around and everything changed. I was stuck in a 600 sq ft apartment which was converted to an office space, a full kitchen/restaurant, living space, a home gym, a dive bar, you name it! I needed an excuse to get out of the house for more than an hour here or there during quarantine so I began training for the Boulder Skyline Traverse Trail.
I trained for this hike by picking a different high peak in Boulder to summit each weekend until eventually checking them all off the list and decided it was time to do the whole thing straight through. I completed this hike on Memorial Day of 2020 and had an absolute blast, the weather was perfect (low 60's) and everything was super green making for beautiful views. I broke down the hike by section below, along with some tips and tricks I picked up along the way, and hope this guide helps for anyone considering taking on this challenge!
High Peaks Summited (In Order Hiking One-Way, Heading North):
South Boulder Peak (8,549 ft)
Bear Peak (8,459 ft)
Green Mountain (8,150 ft)
Flagstaff Mountain (6,983 ft)
Mount Sanitas (6,383 ft)
Beginning the Hike in Eldorado Springs
The first peak you summit on the Boulder Skyline Traverse Trail is South Boulder Peak. The trail technically starts in Eldorado Springs, a town over from Boulder, at the South Mesa Trailhead. I LOVE this trailhead, the views (pictured above) hiking up to the base of the flatirons are gorgeous. Eventually you will reach the Shadow Canyon Trail and hike up the steep and shady canyon to your first destination.
On this trail you gain 2,880 ft of elevation on the four miles up to the top of South Boulder Peak and while it is certainly challenging, this is the most elevation you will gain summiting a single peak. The other peaks you will summit throughout the day will have less of an elevation gain since you are already higher up in the mountains from the previous peaks. This helped me stay motivated early on in the morning to make it up to the top :)
Stop 1: South Boulder Peak Summit
I love this summit! I didn't spend too much time here since I was motivated (at that point at least) to continue on the journey, but other times I've summited here I've stayed for a while to soak in the views. This is the highest peak in Boulder at 8,549 ft and also has the largest summit space so that hikers are able to spread out at the top which is perfect.
In the photos above I'm looking out at Walker Ranch, Eldorado Ski Resort, and RMNP/Brainard Lake area in the far background. I started this hike at 6:30am, made it to the summit at 8:20am, and only encountered one other group at the top.
South Boulder Peak to Bear Peak
This might be my favorite part about the hike because it's the shortest/less strenuous distance between summits! South Boulder Peak and Bear Peak are only 0.6 miles apart via Bear Creek Trail. Once you make your way downhill from South Boulder Peak there is only about a 250 ft elevation gain on the ridge to make it back up to Bear Peak, and since you are so high up for this trail you have 360 degree views of the mountains and plains.
Stop 2: Bear Peak Summit
Out of all the summits, this one is my favorite! It is definitely a rockier summit, and if there are a lot of crowds it can be hard to find a good spot, but thankfully we made it there around 8:45am. While it was starting to fill up more so than South Boulder Peak it was still fairly quiet.
My favorite part about this summit is the views! Just like on South Boulder Peak you have beautiful western facing wide open mountain views (and eastern facing views of Boulder and the plains) but I love how you are also looking down on Green Mountain Summit on the right and South Boulder Peak on the left. We stayed up here for about 20 minutes, had our first trail snack and then prepared for the journey to Green Mountain Summit.
Bear Peak to Green Mountain Summit
This section was a longgg one but I loved every second of it. I had never been on this trail before the Boulder Skyline Traverse, as it follows the backside of the flatirons instead of the front facing trails I was normally used to. This section was not heavily trafficked and it was very cool to see the flatirons from a whole new perspective.
There are 3.85 miles between these two summits, and you will have to hike quite a ways down the mountain to about 7,218 ft only to make your way back up to 8,150 ft. At your lowest elevation you will also pass Bear Creek before making your way back up making for a perfect pit stop!
Stop 3: Green Mountain Summit
I have summited this peak more times than I can count, and it was actually my first hike in Boulder years before I moved here! This summit never gets old, the views in all directions are incredible, and after testing out a number of different trails to get up and down the mountain I haven't run into a bad one.
I made it to the top of Green Mountain Summit at 11:05am and by then I was feeling the mileage. This was where I took a longer break (about 40 minutes) to rest my legs, eat lunch, and soak in the views. This summit is a popular one in Boulder and by the time I made it to the top it was plenty crowded but was able to find a secluded space on the side of the summit to rest before heading down to Flagstaff.
Green Mountain Summit to Flagstaff Mountain
The trail from Green Mountain Summit to Flagstaff Summit is 1.5 miles long and not too strenuous. This is the first time throughout the hike that you loose a decent amount of elevation between peaks. You hike down to 6,726 ft from Green Mountain before heading slightly uphill again another 257 ft to Flagstaff.
This is also the first time throughout the hike that you encounter civilization (aka Flagstaff Road) after spending hours in the mountains with no cell service and not a car in sight. For those that are unfamiliar, Flagstaff Road is a heavily trafficked mountain road in Boulder leading to different trailheads and view points. Stay strong and resist the temptation to beg a driver passing by to drive you back down the mountain! You will cross the main road and continue up the Ute Trail to Flagstaff Summit.
Stop 4: Flagstaff Mountain Summit
The actual peak of Flagstaff Summit is pretty anti climatic (it's in the middle of the woods surrounded by trees with no wide open mountain views) but if you take a quick walk over to the Sensory Nature Trail right by the summit you will be greeted with views like this! I made it to Flagstaff Summit at 12:40pm, stopped to take some photos, and then headed on to the final mountain summit of the day!
Flagstaff Summit to Mount Sanitas
The hike from Flagstaff Summit to just the base of Mount Sanitas was BY FAR the hardest section of the hike for me. Not in terms of elevation gain, since you are losing elevation the majority of the time, but because of the 3.6 mile distance from point A to point B. Don't get me wrong, the views were gorgeous the entire time, but halfway through the trek to Mount Sanitas Trailhead my legs were on fire from the earlier summits of the day.
From Flagstaff Summit you will make your way down the mountain via Flagstaff Trail, eventually connecting with Viewpoint Trail (pictured above). This path has beautiful views of the valley and foothills to the north! Eventually, you will once again make your way to civilization passing through The Eben G Fine Park in downtown Boulder at 5,414 ft. It's worth noting that the park has public restrooms and picnic tables and is a great place to take a quick break before making your way back up to Sanitas!
After loosing over 1,000 ft of elevation from Flagstaff Summit to the Eben G. Fine Park, you will gain it all back hiking back up to the base of Sanitas and eventually the summit! First you will start hiking again on the Red Rocks trail passing a bunch of beautiful rock formations and shortly after you will reach the trailhead for Mount Sanitas.
This is the shortest summit to reach on an individual hike by far. It is only 1.3 miles to the top, and Mount Sanitas is the smallest peak of the five, but do not let that fool you. In just over a mile you gain 1,259 ft of elevation and I've nicknamed the trail nature's stair master since it just goes straight up.
I love summiting Mount Sanitas on its own, and often do this for a weekday workout, but it was VERY challenging to summit after the previous peaks and all the miles in between. I stopped and ate my last round of snacks at the base of the summit by the creek and mentally prepared before heading to the top.
Stop 5: Mount Sanitas Summit
When I finally reached the top at 3:20pm I almost cried tears of joy! I stopped at the summit for about five minutes before heading down to take a quick break and snap a few photos but at that point I was already thinking about my very comfy couch and celebratory victory cocktails. The mile plus trail back down the mountain is steep but I blew right past it, jumped in the car, and drove home. Anddd voila- Boulder Skyline Traverse Trail Complete!
When I arrived back at my apartment I took a much needed shower, sat right down on the couch, ordered uber eats from a local Mexican restaurant, ate tacos and consumed margaritas before passing out at 6pm that evening. :)
Boulder Skyline Traverse Tips & Tricks
Parking
Option A: Since this is a Point A to Point B hike, I would recommend waking up early, driving one car to Sanitas (Centennial TH Parking Lot) and leaving it there for the afternoon. Then drive an additional car to the South Mesa TH in Eldorado Springs where you begin hiking.
*Note- South Mesa TH now requires $5.00/car parking fee.
Option B: You can schedule a ride(s) in advance for pick up and drop off or you can drive one car first thing in the morning South Mesa TH and then order an uber/lyft once you make it back to Mount Sanitas TH. The Sanitas Trailhead does have cell service to order a ride or call a friend for a ride!
Food & Beverage
This hike is strenuous so plan on bringing plenty of water (especially during the summer months) and snacks high in protein to refuel. I had one full meal on Green Mountain and two additional snack breaks throughout the hike and it was much needed to reenergize.
What to Wear
Bring layers! The summits have cooler weather at the top and I was constantly taking off/putting back on my sweatshirt. Wear sturdy hiking boots with ankle support since there are rocky sections throughout the hike. I also found having leggings with pockets was super helpful so that I could easily access my phone for photos whenever I needed it on the trail.
Additional Items to Bring
-Sunscreen
-Chapstick
-Backup phone charger
-Electrolyte packets to mix in your water.
-Extra pair of socks in case yours get muddy or wet and you need to swap
Best Time of Year to Complete
This trail can be hiked at any point in the year (in the winter you would need the appropriate gear for snow/ice conditions). I personally recommend hiking this in the spring or fall when the temps are cooler then summer but you typically won't be encountering any snow or ice at the top.
With quarantine timing, I ended up hiking this trail in late May on a cooler day where the temps were in the low 6Os and the conditions were PERFECT! I also waited for all the trees to be super green making the views even better. Hiking this right when all the leaves are changing colors during the fall in October would be beautiful as well!
Overall Takeaways From the Hike
I loved this hike and would definitely recommend it to anyone who is considering it. The trail is challenging but so rewarding with beautiful views the entire way! I personally do not want to hike this again, but would be open to hiking a similar type of trail in a different location to be able to check another challenging route off of the list. However, I loved the South Boulder to Bear Peak, to Green Mountain loop on it's own and would do that again or would do the Flagstaff Summit to Mount Sanitas Summit trail again- just not all at once!
I also thought it was very beneficial to train for this hike beforehand by summiting the five peaks individually. This helped me to become familiar with the trail system and gave me something to look forward to leading up to the hike!
Happy Trails!
-Casey
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