Claustral Canyon.

Photograph by Carsten Peter Cascades of mammoth ferns flourish in the humid air trapped between the narrow walls of Claustral Canyon. First explored in 1963, the formation was named for its claustrophobia-inducing passages and ranks among the region’s most visited canyons. via Buzzfeed Australia.

http://derwombat.net/2015/12/11/claustral-canyon-blue-mountains/