Now that you’re traveling in the Redwall, repetitive neck strain is a real possibility. From river level, it’s fascinating to gaze up and examine the cliffs right and left for natural features like pockets, caves, arches, and alcoves, formed where water has dissolved softer deposits in the limestone. Some alcoves protect Ancestral Puebloan dwellings built a millennium ago, such as the ruins at the mouth of South Canyon, which enters Marble Canyon at mile 31.

River runners often stop to explore South Canyon’s polished limestone narrows. Stanton and the remainder of his crew abandoned their first attempt to run the Colorado and used South Canyon to return to the rim, stashing their gear in a dry limestone cave nearby.

Just downstream, Robert Brewster Stanton’s Cave is a veritable treasure trove where scientists have found the bones of a Pleistocene-era giant sloth and split-twig figurines from the Archaic period, as well as the gear left by Stanton’s expedition. (The cave is closed to visitors.)

A little farther downriver, Vaseys Paradise, a lush green spring-fed oasis, decorates the canyon’s west wall (river right). John Wesley Powell named this beautiful feature for a botanist who accompanied him on earlier expeditions. Crimson and yellow monkey-flower, ferns, watercress, and other species thrive in this natural garden. River parties often stop here, but unless you know what poison ivy looks like, be careful where you frolic.

The Park Service would prefer you didn’t frolic here at all because human activity may impact one of Grand Canyon’s endangered species, the Kanab ambersnail, a tiny land snail with only two native habitats, Vaseys Paradise and a meadow near Kanab, Utah, where it is threatened by commercial development.