Lion's Lair Trail
Lion's Lair is a 2.7-mile trail that climbs 1,228 feet to the Mount Sanitas summit on steady switchbacks instead of rock steps, which makes it the gentler way up Boulder's most-climbed peak, though dogs are prohibited on it.
Outdoor Boulder › Destinations › Lion's Lair Trail
Lion's Lair Trail quick facts
- Managing agency
- City of Boulder Open Space and Mountain Parks (OSMP).
- Distance
- 2.70 miles, per OSMP, one way to the Mount Sanitas summit ridge. Figure roughly 5.4 miles round trip if you go up and back the same way.
- Elevation gain
- 1,228 feet, per OSMP.
- Difficulty
- Medium/Hard, per OSMP, meaning a mix of medium and hard segments. That's a notch easier than the Mount Sanitas Trail itself, which OSMP rates Hard.
- Trail width
- 3 to 6 feet, with smooth surfaces and gentle switchbacks.
- Allowed uses
- Hikers only. No bikes, no horses.
- Dog policy
- Dogs are prohibited. Not leashed, not Voice and Sight, prohibited. This is one of the few OSMP trails near town where you cannot bring a dog at all.
- Parking
- Centennial Trailhead, 301 Sunshine Canyon Road: 31 standard spaces, 2 ADA spaces, restrooms, no fee. Open 5 a.m. to 11 p.m. High use, more than 200 visits a day.
- Watch for
- OSMP notes mountain lion activity along this corridor, along with black bears and mule deer in the area. The trail name is not decorative.
The one thing to know first: no dogs
OSMP prohibits dogs on Lion's Lair. Not leashed, not with a Voice and Sight tag, not at all. This surprises people because dogs are welcome on most of the trails around Mount Sanitas, including the Mount Sanitas Trail and the Sanitas Valley Trail that leave from the same parking lot. If you show up with a dog, you'll need to pick a different route, so it's worth knowing before you're standing at the trailhead.
Why people choose Lion's Lair
Mount Sanitas is the peak everyone in Boulder climbs, and the standard Mount Sanitas Trail up its east ridge is a brutal stair-stepper: roughly the same elevation in about a third of the distance, over rock steps that punish knees on the way down. Lion's Lair does the same job differently. OSMP describes gentle switchbacks through ponderosa forest, a steady grade, and smooth surfaces, and it spreads 1,228 feet of climbing across 2.7 miles.
The trade is time. You'll be out roughly twice as long. What you get is a hike you can hold a conversation on, footing that doesn't demand constant attention, and a much kinder descent. Trail runners love it for exactly those reasons.
The classic loop
The move most locals make is to go up Lion's Lair and come down the Mount Sanitas Trail, or the reverse if you'd rather get the steep part over with early. Either way you end up back at the Centennial Trailhead without repeating a step, and you get both characters of the mountain in one morning. Going up the steep side and down the gentle side is the friendlier version for most knees.
The view, and the forest
OSMP puts it well: as you ascend, the views of high peaks and rolling forests get better and better. That's the real difference from the east-ridge route, which stares at town the whole way. Lion's Lair works around the back side of the mountain, so you're looking at the Continental Divide and forested foothills rather than at rooftops. There's a lot of wildlife along the corridor, and OSMP suggests bringing binoculars for the birding.
About the name
OSMP notes mountain lion activity along this corridor. Boulder's foothills are lion country generally, and this quiet, forested north-facing slope is good habitat. Encounters are genuinely rare. The habits that matter: go with someone when you can, keep kids where you can reach them, skip the solo dusk run with headphones, and if you do see a lion, make yourself big, make noise, and back away slowly instead of running. Black bears and mule deer are around too.
Parking and the trailhead
Start from the Centennial Trailhead, 301 Sunshine Canyon Road, on the south side of Sunshine Canyon just west of the Sanitas access point. Thirty-one standard spaces, 2 ADA spaces, restrooms, four picnic tables, no fee, open 5 a.m. to 11 p.m. It's classed high use, more than 200 visits a day, and it's shared with everyone heading up Sanitas, Anemone, and Red Rocks, so arrive early on a weekend or plan to circle. There are no bikes in this area at all: OSMP states the Centennial area has no trails that allow mountain biking. Buses SKIP, 208, and Y stop at Broadway and Mapleton, nine blocks east, and every OSMP trailhead has bike racks.
When to hike it
The forest cover that makes Lion's Lair pleasant in July also means it holds snow and ice well into spring on the north-facing sections. Microspikes are a reasonable thing to carry from about November through April. In summer, the shade makes this the more comfortable of the two Sanitas routes by a wide margin, especially in the afternoon. Watch the weather in summer either way: the summit ridge is exposed, and Boulder afternoon storms build fast. Our thunderstorm safety guide covers the timing.
Nearby trails and guides
- Mount Sanitas: the steep east-ridge classic, and the other half of the loop.
- Sanitas Valley Trail: the flat, wide valley option, dogs welcome.
- Anemone Loop Trail: another climb from the same lot.
- Best trail running near Boulder: where this one really shines.
- Hiking with dogs in Boulder: which trails actually allow them.
Lion's Lair Trail FAQ
Can you bring dogs on the Lion's Lair Trail?
No. OSMP prohibits dogs on Lion's Lair entirely, and it's listed for hikers only. A City of Boulder Voice and Sight tag does not help here. If you're hiking Mount Sanitas with a dog, use the Mount Sanitas Trail or the Sanitas Valley Trail instead, where dogs are allowed on leash or with a Voice and Sight tag.
Is Lion's Lair easier than the Mount Sanitas Trail?
Gentler, yes. Shorter, no. OSMP rates Lion's Lair medium to hard and the Mount Sanitas Trail hard. Lion's Lair spreads 1,228 feet of climbing over 2.7 miles of switchbacks with smooth tread, while the Sanitas Trail throws similar elevation at you in about a mile of rock steps. If your knees dislike stairs, Lion's Lair is the friendlier way to the same summit.
How long is the Lion's Lair Trail?
OSMP publishes 2.70 miles with 1,228 feet of elevation gain. That's one way to the Mount Sanitas summit area, so an out-and-back is roughly 5.4 miles. Many people go up Lion's Lair and down the Mount Sanitas Trail to make a loop back to the same trailhead.
Are there really mountain lions on Lion's Lair?
OSMP notes mountain lion activity along this corridor on its own trail page, and black bears and mule deer live in the area too. Sightings are rare and attacks are far rarer, but the sensible habits apply: hike with others when you can, keep children close, don't run alone at dawn or dusk with headphones in, and if you do meet one, make yourself large and back away rather than running.
Where do you park for Lion's Lair?
The Centennial Trailhead at 301 Sunshine Canyon Road, with 31 standard spaces, 2 ADA spaces, restrooms, and no parking fee, open 5 a.m. to 11 p.m. It's a high-use trailhead serving Sanitas, Anemone, and Red Rocks as well, so on summer weekend mornings it fills early. The SKIP, 208, and Y buses stop at Broadway and Mapleton, about nine blocks east.
What is the Lion's Lair Trail like to hike?
OSMP describes gentle switchbacks through ponderosa forest, a steady grade, and smooth surfaces, and that's fair. It's a rhythm hike rather than a scramble: you settle into a pace and grind out the elevation while the views of the high peaks and the rolling forest open up behind you. It was added to the OSMP system in 2015, so it's modern trail-building and it feels like it.
Sources
Facts on this page are drawn from these authoritative sources:
Last checked . We verify trail facts against the managing agency, and we say so when a figure isn't published.