“The obvious question is, why isn’t the river frozen? Does anyone know the answer?” The eight of us huddled in our down parkas and snow boots on the banks of the river look at the water tumbling between banks thick with snow and shrug helplessly. Even the Canadians who live just forty miles away have no ideas. Given the below-zero temperature and the knee-deep snow, it certainly seems a mystery.
The explanation, it turns out, is the key to why the Maligne Canyon Ice Walk — the outdoor adventure on which we’ve just embarked — is so utterly and completely unique. In fact, there’s nowhere else in north America where you can see what we’ve donned rubber boots and cleats to see here, which is why we’ve come all the way from various parts of the U.S. and Canada to see it. (See below for practical tips on how to visit Maligne Canyon and Jasper National Park.)

The answer, when it comes, is geology. Geology having to do with underground springs and fissures in the rock. This area of Jasper National Park, which also contains Medicine Lake, a lake famed for disappearing mysteriously at the height of the summer glacier melt despite having no outlet, is riddled with underground springs. And of course underground springs don’t freeze. So even during Rocky Mountain winters during which temperatures can hover around zero for months at a time and entire lakes freeze solid within weeks, the Maligne River does not freeze. Or at least it doesn’t freeze solid.

Instead, the water freezes bit by bit in shallow layers of ice that builds itself into waves, swirls, sheets, and waterfalls that are spectacular to see. It’s as if nature put on an ice carving show deep in a canyon with nothing but the foxes, elk and bighorn sheep to witness it. There are waterfalls of ice 30 feet high, icicles taller than I am, and caves walled by solid ice that drips bit by bit from rock overhangs. Going inside the caves, accessed through tunnels of ice,  is like seeing what it would look like inside a gigantic diamond.

The ice isn’t the only thing about hiking Maligne Canyon in winter that’s magical. The other thing that feels magical is that you can be here at all. As summertime visitors to Jasper know well, you can’t get down to the Maligne River  when it’s flowing. The trail skirts the tops of the cliffs, and the closest you can get to the water thundering through the sheer rock walls of the canyon is to peer down on it from above. But in winter, as layers of ice cover the top of the river (the water’s still flowing underneath) you can walk up the canyon itself, gazing in awe up at sheer granite cliffs that tower above, looming so closely over the river they almost meet above.

Our guide, Chris Roy of Overlander Trekking and Tours, points out the line of moss indicating summer high water levels well above head height, leaving us to imagine the force of the water as it’s channeled by the narrow rock walls around and above us. Even the part of the river that is navigable is classified by kayakers a Class 5, safe only for the most experienced pros. This means the Maligne Canyon Ice Walk is an ephemeral treat; guides start taking people up the canyon at the beginning of December, when they’ve deemed the ice solid enough to stand on, and stop at the end of March when it gets too soft.

As part of Jasper National Park, Maligne Canyon is open to all and the road to the trailhead is plowed, so you don’t have to come with a guide. But the trail down to the canyon would be hard to find without a local to show you so if you do come alone, get good directions first. And don’t try it without knee-high rubber boots and ice cleats, necessary to navigate areas where new springwater hasn’t frozen yet and to prevent slipping on the sheets of ice.

So for first time visitors, I’d recommend a guided trip; the three-hour treks are led by two outfitters, Overlander Trekking and Jasper Adventure Centre. Pickups are available from your hotel, so there’s no need to drive if snow driving isn’t your thing.