Best hard trails in Boulder

4.7(86,097 reviews)

Explore the most popular challenging trails near Boulder with hand-curated trail maps and driving directions as well as detailed reviews and photos from hikers, campers and nature lovers like you.

Top trails

#1 - Royal Arch Trail

4.8(18191)

•Hard

•3.3 mi

Located just off Baseline Road, this fantastic hike features great views and gives you the opportunity to get up close and personal with the incredible rock formations that have come to characterize the city of Boulder. This trail starts near the ranger cottage at the Chautauqua Park Trailhead. Start hiking along the Bluebell Trail and head south. You could also follow the Chautauqua Trail and eventually meet up with this route at the Bluebell Shelter by way of the Bluebell-Baird...

#2 - Mount Sanitas, East Ridge, and Sanitas Valley Loop

Mount Sanitas is a must-do hike if you’re in Boulder! The trailhead is centrally located close to downtown Boulder. You can walk from downtown to the Centennial Trailhead on Sunshine Canyon Drive from downtown Boulder. The trailhead has a small parking area that gets full quickly in the morning, so it’s best to arrive early. If it’s full, there is more parking on the road. From the trailhead, you'll continue north on Mount Sanitas Trail. Eventually you’ll reach the summit of Mount Sanitas....

#3 - First and Second Flatirons Loop

4.8(5038)

•Hard

•2.7 mi

The First and Second Flatirons Loop is a short but steep hike that takes you to two of the most popular Flatirons in Boulder Open Space. This route can be accessed by both Chautauqua Trailhead as well as Enchanted Mesa Trailhead which is just to the east. There are restrooms and a tourist information center at the trailhead. This loop is popularly known as the First and Second Flatirons Loop. It travels along the Chautauqua Trail, First and Second Flatirons Trail, and the Bluebell Road...

#4 - Bear Peak via Shanahan Ridge

This hike can be completed year round, though it can be covered in snow after a snowfall. Depending on the time of year, there are creeks and ponds for water. From either Cragmoor or Shanahan at Lehgh trailheads, rise steadily up through open ponderosa pine forest on the North Fork Shanahan trail heading west. The trail narrows from a road to a single track as you cross the Mesa Trail. It turns right at the base of a steep sandstone slab and then crosses Fern Canyon to reach the Fern Canyon...

#5 - Mount Sanitas Peak Trail

Mount Sanitas is a must-do hike if you’re in Boulder. You can basically walk to the Centennial Trailhead on Sunshine Canyon Drive from downtown Boulder. The peak offers beautiful views, with enough challenge to get you sweating. The trailhead has a small parking area that gets full quickly in the morning, so it’s best to arrive early. If it’s full, there is more parking down the road. From the trailhead, continue north on Mount Sanitas Trail. This trail has a steady incline along a rocky,...

#6 - Green Mountain via Chautauqua, Amphitheater, and Gregory Canyon Loop

This route is a popular peak hike providing views of the Indian Peaks and Boulder. On this route, you'll be hiking along the Chautauqua, Meadow, Saddle Rock, Amphitheater, E.M. Greenman, West Ridge, Ranger, Gregory Canyon, and Baseline Trail. Parts of the route can get confusing since there are many intersections. It is a good idea to download your offline map ahead of time to help with navigation.

#7 - Chautauqua Trail via 6th Street Connector

Chautauqua Trail via 6th Street Connector is a short but steep trail that features the perfect mix of scenery and challenge. Conveniently located close to the city of Boulder, this hike is popular with both locals and tourists. Hikers can enjoy traversing through grasslands and soaking up views of the sandstone slabs above. Some sections are very steep and require rock scrambling to reach the overlook and enjoy the far-reaching views of the Boulder cityscape below. This route's inclines...

#8 - Bear Peak via NCAR

4.8(2209)

•Hard

•5.7 mi

This hike leads to Bear Peak via the NCAR Trail, taking you up to Boulder's second-tallest peak, which stands at 8,461 feet. Be prepared for a steep and rocky finish with a scramble to the summit. The effort is well worth it, as the views from the top are spectacular. It’s often windy and cold at the summit, so wearing layers is recommended. If you're planning a winter hike, don’t forget to bring spikes.

#9 - Mount Sanitas Trail Loop

This is an iconic trail in Boulder. Mount Sanitas offers stunning views overlooking the city and features amazing rock formations. The trail's scenery varies, with ridges, meadows, and rough boulders. It has steep inclines and rocky scramble-like conditions. The parking at the Centennial Trailhead is limited, so it's recommended to come earlier.

#10 - Gregory Canyon, E.M. Greenman, Saddle Rock and Amphitheater Loop

Dogs are allowed on most of this loop, but they are not allowed on the EM Greenman Trail portion of this loop.

Showing results 1–10 of 53

Explore more trails

Trail reviews for Boulder

Nicole Pezzino

May 20, 2025•Hiking

Great views

Whaaatttt a hike!!! The trail going up to the Arch was spectacular. Started off with a beautiful grass field leading into the magnificent mountains. As I turned the corner, I saw the height/elevation rise and the rocks get bigger. The path was well paved and the rocks were really helpful to step on going up. After the last few rocks we turned the corner and to my left was the Arch! My jaw dropped!! The view from the top of this mountain was like no other. I am already looking forward to doing this hike again!

Royal Arch Trail

AJ Ponte

May 18, 2025•Hiking

Great conditionsGreat views

Beautiful lil wildflowers this time of year

Difficulty: Hard

Mount Sanitas, East Ridge, and Sanitas Valley Loop

Peter Roberge

May 20, 2025

Easy to parkGreat conditionsGreat views

Went rock climbing with an experienced friend to belay and guide me. Definitely not something to take lightly! I did alright for a beginner, however my fiancée is afraid of heights and had a brief moment of panic that could’ve gone awry. Humbling. The trail took a bit out of my Urban East Coast lungs as well with the elevation for a bit but it’s beautiful and fairly chill for casual hikers like myself.

First and Second Flatirons Loop

Ultimate Kilimanjaro

May 20, 2025•Hiking

Great conditions

Fun hike. Five minute scramble at the top and worth doing. Great views of Boulder. Pretty rocky trail but runnable near the bottom.

Difficulty: Hard

Bear Peak via Shanahan Ridge

Samantha Goldin

May 15, 2025•Hiking

Great conditionsGreat views

i want whatever crack the boulder trail runners have

Difficulty: Hard

Mount Sanitas Peak Trail

Wylie Ewing

May 16, 2025•Hiking

Got there early so parking and crowds were low. Crowds did pick up as i sat on the summit of Green Mountain. Nice loop. Too many dogs and flatlanders that dont really understand trail etiquette but thats is to be expected around the flatirons. I combined this loop with Royal Arch loop for a solid day. All and all a great day.

Green Mountain via Chautauqua, Amphitheater, and Gregory Canyon Loop