Trips Places Foods Stories Newsletters

Take your next trip with Atlas Obscura!

Our small-group adventures are inspired by our Atlas of the world's most fascinating places, the stories behind them, and the people who bring them to life.

Visit Adventures
Trips Highlight
Puglia Italy - Matera
Italy • 8 days, 7 nights
Southern Italy: Castles, Caves & Coastal Treasures in Puglia
from
Turkmenistan Gates of Hell Darvaza crater
Turkmenistan • 10 days, 9 nights
Turkmenistan & the Gates of Hell
from
View all trips
Top Destinations
Latest Places
Most Popular Places Random Place Lists Itineraries
Add a Place
Download the App
Top Destinations
View All Destinations »

Countries

  • Australia
  • Canada
  • China
  • France
  • Germany
  • India
  • Italy
  • Japan

Cities

  • Amsterdam
  • Barcelona
  • Beijing
  • Berlin
  • Boston
  • Budapest
  • Chicago
  • London
  • Los Angeles
  • Mexico City
  • Montreal
  • Moscow
  • New Orleans
  • New York City
  • Paris
  • Philadelphia
  • Rome
  • San Francisco
  • Seattle
  • Stockholm
  • Tokyo
  • Toronto
  • Vienna
  • Washington, D.C.
Latest Places
View All Places »
Pinal Airpark
Note the chrysanthemum crests.
Hachiman Bridge
Clarendon War Memorial.
Clarendon War Memorial
This fried chicken is one of Bangkok’s most famous.
Gai Tord Jae Kee
Latest Places to Eat & Drink
View All Places to Eat »
Order a flight of infused ya dong shots.
Tep Bar
Thai-Chinese makes up Bangkok’s largest diaspora.
Nai Ek Roll Noodle
This fried chicken is one of Bangkok’s most famous.
Gai Tord Jae Kee
Chefs Aruss Lerlerstkull and Atcharaporn Kiatthanawat lean into regional traditions.
Charmgang
The khao soi at Gedhawa comes with a rich, coconutty broth.
Gedhawa
Recent Stories
All Stories Video Podcast
Most Recent Stories
View All Stories »
Haleakalā National Park’s summit region, shrouded in the pre-dawn fog.
Beware the Legends Behind These National Park Souvenirs
7 days ago
For Aguilar-Carrasco, nature is a powerful reminder of the interconnectedness of all life.
How Can National Parks Be Made Accessible to All? AO Wants to Know.
8 days ago
Podcast: Finding ‘The Great Gatsby’ in Louisville
9 days ago
Here’s which treats you can safely lug home without risking a fine.
Dear Atlas: What International Food Can I Legally Bring Into the U.S.?
10 days ago

No search results found for
“”

Make sure words are spelled correctly.

Try searching for a travel destination.

Places near me Random place

Popular Destinations

  • Paris
  • London
  • New York
  • Berlin
  • Rome
  • Los Angeles
Trips Places Foods Stories Newsletters
Sign In Join
Places near me Random place
All Canada Alberta Castleguard Cave
AO Edited

Castleguard Cave

Canada’s longest cave system is home to creatures found nowhere else on the planet, as well as rare cave pearls.

Alberta

Added By
Danielle Hallock
Email
Been Here
Want to go
Added to list
Flagged soda straws point towards the cave’s entrance.   Ian McKenzie / CC BY 2.5
Flagged soda straws point towards the cave’s entrance.   Ian McKenzie / CC BY 2.5
Spelunkers venture down a fissure.   Ian McKenzie / CC BY 2.5
The gate’s only entrance is barred.   James Heilman / CC BY 3.0
The cave’s only entrance can be found at the northern end of the park.   James Heilman / CC BY 3.0
Been Here
Want to go
Added to list

About

Castleguard Cave is rife with superlatives. It’s the longest cave system in Canada at 13 miles (21 kilometers), as well as the only non-ice cave that sits beneath a current glacier, called the Columbia Icefield, which is the largest ice mass left in the Rocky Mountains. The result is a grand subterranean world that combines both cave and glacier attributes in a combo hardly seen before. In addition to calcium stalactites, stalagmites, and long soda straws, the cave also hosts extremely rare cave pearls, which are like spheres of calcium salt. 

Access to the cave requires a permit from the national park, as it’s quite dangerous. Teams are only able to do so in winter, when the cave is less likely to flood and a pool of water near the entrance freezes thick enough to be able to cross. After reaching the cave entrance in the meadow of a valley, cavers drop down a 26-foot shaft, then belly-crawl over the ice pond to reach a pool of water in the warmer interior of the cave. 

Scuba diving is then required to get any further, to a tunnel that is so perfectly round it’s referred to as “The Subway.” The only known paths burrow deep below Castleguard Mountain until they finally terminate at the glacier itself, completely blocked by the ice that’s around 650 to 1,000-feet thick. That means there’s only way in and out of the 13-mile cavern, making it the world’s furthest exit in a cave, so quick rescues are not an option. In the summer months, glacier melt floods the cave, pouring rapidly down a shaft called “Boon’s Blunder” and out the only entrance. 

A few areas of the cave are named after Mike Boon, an intrepid caver. But because Boon explored Castleguard in 1970 without permission of Parks Canada, officials did not allow details of his journey to be published, so little is publicly known about his mysterious descent and whatever “blunder” happened to earn the flooding shaft its name. 

Research teams have discovered a few animals that depend on this cold, dark environment, including some small pack rats and two blind, translucent shrimp creatures. One of those crustaceans, called Castleguard Cave Amphipod (Stygobromus canadensis), is found nowhere else in the world. Scientists speculate that this animal survived the ice age by sheltering in this cave. It’s a place that is still being explored by researchers and spelunkers looking to put their name on potentially new expansions yet to be discovered.

Related Tags

Adventure Caves National Parks

Know Before You Go

Entrance to the cave is severely restricted, but if you're one of the lucky few to get a permit, be prepared for the adventure of a lifetime. 

Community Contributors

Added By

daniellehallock

Published

April 24, 2025

Edit this listing

Make an Edit
Add Photos
Castleguard Cave
Improvement District No. 9
Alberta, AB T0L 1E0
Canada
52.168076, -117.100299

Nearby Places

Athabasca Glacier

Jasper, Alberta

miles away

Columbia Icefield

Alberta

miles away

Columbia Icefield Skywalk

Jasper, Alberta

miles away

Explore the Destination Guide

Photo of Alberta

Alberta

Canada

Places 81
Stories 5

Nearby Places

Athabasca Glacier

Jasper, Alberta

miles away

Columbia Icefield

Alberta

miles away

Columbia Icefield Skywalk

Jasper, Alberta

miles away

Explore the Destination Guide

Photo of Alberta

Alberta

Canada

Places 81
Stories 5

Related Places

  • Stalactites in King Solomon’s Cave

    Liena, Australia

    King Solomon's Cave

    A limestone cave filled with impressive formations in Mole Creek Karst National Park.

  • Inside.

    Borrowdale, England

    Millican Daltons Caves

    It's believed a local adventurer spent 50 years living inside this cave.

  • The Den of Nargun when water is scarce.

    Iguana Creek, Australia

    Den of Nargun

    Mind the rock monster at this cave.

  • Cave and Basin National Historic Site in Banff National Park.

    Banff, Alberta

    Cave and Basin National Historic Site

    The natural hot spring that was integral to the creation of Canada's first national park.

  • Chinhoyi Caves

    Chinhoyi, Zimbabwe

    Chinhoyi Caves

    The stunningly blue waters of these beautiful caves also have a violent past.

  • Rock Art at Nino Konis Santana National Park.

    Timor-Leste

    Rock Art at Nino Konis Santana National Park

    Ancient images hide within the park's caves.

  • Ein Avdat pool and waterfall.

    Be'er Sheva, Israel

    Ein Avdat

    A magical oasis in the middle of the Negev Desert.

  • Entrance to the Cueva de las Lechuzas.

    Las Palmas, Peru

    Cueva de Las Lechuzas

    A jungle cave in Peru of unknown depths, otherworldly sounds, and strange nocturnal birds that navigate by echolocation.

Aerial image of Vietnam, displaying the picturesque rice terraces, characterized by their layered, verdant fields.
Atlas Obscura Membership

Become an Atlas Obscura Member


Join our community of curious explorers.

Become a Member

Get Our Email Newsletter

Follow Us

Facebook YouTube TikTok Instagram Pinterest RSS Feed

Get the app

Download the App
Download on the Apple App Store Get it on Google Play
  • All Places
  • Latest Places
  • Most Popular
  • Places to Eat
  • Random
  • Nearby
  • Add a Place
  • Stories
  • Food & Drink
  • Itineraries
  • Lists
  • Video
  • Podcast
  • Newsletters
  • All Trips
  • Family Trip
  • Food & Drink
  • History & Culture
  • Wildlife & Nature
  • FAQ
  • Membership
  • Feedback & Ideas
  • Community Guidelines
  • Product Blog
  • Unique Gifts
  • Work With Us
  • About
  • FAQ
  • Advertise With Us
  • Advertising Guidelines
  • Privacy Policy
  • Cookie Policy
  • Terms of Use
Atlas Obscura

© 2025 Atlas Obscura. All Rights Reserved.