Mallory Cave
Mallory Cave is a short, steep hike and scramble from the NCAR Trailhead in Boulder, and the cave itself is closed to entry year-round to protect a colony of threatened bats. You can hike up to near the cave entrance, but you cannot go inside.
Outdoor Boulder › Destinations › Mallory Cave
Mallory Cave quick facts
- Distance
- Short. OSMP describes Mallory Cave as a short trail off the Mesa Trail and NCAR Trail junction and does not publish an official mileage. Plan for a short but steep out-and-back.
- Elevation gain
- OSMP does not publish a figure. The route climbs steeply from the NCAR Trailhead and finishes with a scramble up a solid rock notch to near the cave entrance.
- Difficulty
- Steep, with a short rocky scramble near the top. Use caution in winter if snow or ice are present.
- Trailhead
- NCAR (National Center for Atmospheric Research), at the west end of Table Mesa Drive. Open 5 a.m. to 11 p.m. daily. Large parking lot; restrooms are inside the NCAR building during its open hours.
- Cave access
- Closed. The cave itself is closed year-round to protect a colony of threatened Townsend's Big-eared Bats and to reduce the chance of people introducing white-nose syndrome. A buffer around the cave is also closed April 1 through October 1. You can still hike up to near the cave entrance when the approach is open.
- Dogs
- On NCAR (federal) property near the trailhead, all dogs must be on a hand-held leash. Beyond NCAR property, dogs must be leashed unless they meet the Voice and Sight control standard and display a City of Boulder Voice and Sight tag. Watch for signs at trail junctions.
- Best season
- October through March, when the full approach to the cave entrance area is open (part of the trail is closed April 1 through October 1). Use caution in winter for snow and ice.
Mallory Cave at a glance
Mallory Cave is a short trail in the Flatirons above the National Center for Atmospheric Research (NCAR) in south Boulder. It comes off the junction of the Mesa Trail and the NCAR Trail, climbs steeply, and ends with a scramble up a solid rock notch to near the cave entrance. It's a small, punchy objective rather than a long day out. The catch is the reason many people come: you can reach the entrance area, but the cave itself is closed to entry.
Is Mallory Cave closed?
Yes, to entry. In OSMP's own words, the cave itself is closed year-round to protect the bats. Mallory Cave is one of a few OSMP caves closed permanently to human use to reduce the chance of people introducing white-nose syndrome, a disease that can sharply reduce bat populations. On top of that permanent closure, a buffer around the cave is closed April 1 through October 1 to protect the bats during their sensitive season. The hike up to near the cave entrance is still open, but going inside is not allowed at any time of year.
Why the cave is protected
The cave provides habitat for the threatened Townsend's Big-eared Bats, a sensitive species with only a small number of known breeding colonies in Colorado. Keeping people out of the cave protects that colony directly, and it also helps keep white-nose syndrome from being carried in on clothing or gear. If you make it to the entrance area, the respectful move is simple: look, don't enter, and don't linger at the opening.
The NCAR Trailhead and parking
The trail is reached from the NCAR Trailhead at the west end of Table Mesa Drive, at the National Center for Atmospheric Research. The trailhead is open 5 a.m. to 11 p.m. daily and has a large parking lot, which fills on nice weekends, so come early. Restrooms are inside the NCAR building during its open hours. Bicycles are not allowed on the trails in this area.
The hike and the scramble
From the trailhead you'll link onto the Mesa Trail and NCAR Trail before the Mallory Cave junction, then climb steeply. The final stretch is a hands-on scramble up a rock notch to near the cave entrance, so wear shoes with grip and take your time on the rock. Part of the trail is only open October through March, which lines up with the April-through-September buffer closure, so the full approach to the cave entrance area is really a fall-and-winter outing. Use caution in the winter months if snow or ice are present.
Dogs on the Mallory Cave trail
Near the trailhead, on NCAR (federal) property, all dogs must be on a hand-held leash. Once you're beyond NCAR property, OSMP's usual rule applies: dogs must be leashed unless they meet the Voice and Sight control standard and wear a City of Boulder Voice and Sight tag. Dog regulations change from trail to trail here, so watch for the signs at trailheads and trail junctions, and pack out what your dog leaves behind.
Best season and time to go
Because of the seasonal buffer closure, the full approach to the cave entrance area is open October through March. That makes late fall through early spring the window for reaching the entrance, with clear, cold mornings often the nicest time on the rock. Whenever you go, remember the cave stays closed to entry all year, so plan the trip around the hike and the view, not going inside.
Nearby trails and guides
- NCAR and the Mesa Trail: the trailhead and trail network Mallory Cave branches off of.
- Wildlife safety in Boulder: bats, bears, mountain lions, and how to share the trails responsibly.
- All hikes in Boulder: the full hiking hub, sorted by difficulty.
Recommended nearby
A few local spots we'd point a Mallory Cave morning toward.
[CLIENT SLOT: featured gear shop near NCAR / South Boulder]
[One honest line: grippy shoes or a daypack for the scramble.]
[CLIENT SLOT: featured cafe near Table Mesa]
[One honest line: coffee or a bite before or after the hike.]
[CLIENT SLOT: featured local hiking or scrambling guide]
[One honest line: a guided intro to Flatirons scrambling.]
Mallory Cave FAQ
Can you go inside Mallory Cave?
No. In OSMP's words, the cave itself is closed year-round to protect the bats. Mallory Cave is one of a few OSMP caves closed permanently to human use to reduce the chance of people introducing white-nose syndrome, a disease that can devastate bat populations. You can hike up to near the cave entrance, but you cannot enter the cave.
Why is Mallory Cave closed?
The cave provides habitat for the threatened Townsend's Big-eared Bats. OSMP closed it to entry to protect that colony and to keep people from spreading white-nose syndrome into the cave. A buffer around the cave is also closed April 1 through October 1 to protect the bats during their sensitive season.
Is the Mallory Cave trail open?
The hike toward the cave entrance area is open, but part of the trail is only open October through March. A buffer around the cave is closed April 1 through October 1, so the final approach to the cave entrance is a fall-and-winter option. The cave itself stays closed to entry all year.
Where does the Mallory Cave trail start?
From the NCAR Trailhead at the west end of Table Mesa Drive, at the National Center for Atmospheric Research. The trail comes off the junction of the Mesa Trail and the NCAR Trail, then climbs steeply and finishes with a scramble up a solid rock notch.
Can you bring a dog to Mallory Cave?
Yes, with rules. On NCAR (federal) property near the trailhead, all dogs must be on a hand-held leash. Beyond NCAR property, dogs must be leashed unless they meet OSMP's Voice and Sight control standard and wear a City of Boulder Voice and Sight tag. Watch for dog-regulation signs at trailheads and trail junctions.
Sources
Facts on this page are drawn from these authoritative City of Boulder OSMP sources: