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Just before it joins the Vermillion River, Tokumm Creek tumbles through a slot canyon--a gorge which is deeper than it is wide.
In places it's only a couple metres wide, but tens of metres deep.
Called Marble Canyon for its bright-colored limestone walls, it's quite the visual treat, complete with a thundering waterfall at the top of the narrows. A mostly level path traces the rim of the canyon and includes a few bridges, offering many views into the depths.
Rails protect the edge, so it's safe for all ages and at all times of year, though traction devices are recommended in winter.
When the creek freezes, it's possible to walk the ice within the canyon, viewing it all from below. Sources: https://www.pc.gc.ca/en/pn-np/bc/kootenay/activ/randonnee-hike/courte-short https://hikingwithbarry.com/2013/10/28/marble-canyon-kootenay-national-park-hiking-bc