David Brower visited Glen Canyon shortly after the decision to build the dam, and "realized once he arrived that this was not a place for a reservoir". Glen Canyon's springs, side canyons, and intricately sculpted rock formations were home to such features as Music Temple and Cathedral in the Desert, a giant cave-like natural amphitheater with a waterfall at its center. The Colorado River flowed gently across the bottom of the canyon, in sharp contrast to the roaring rapids upstream in Cataract Canyon and downstream in the Grand Canyon. After his groundbreaking 1869 expedition, John Wesley Powell had named Glen Canyon for its characteristics: "So we have a curious ensemble of wonderful features – carved walls, royal arches, glens, alcove gulches, mounds and monuments. From which of these features shall we select a name? We decide to call it Glen Canyon." In addition to its variegated rock formations, Glen Canyon supported a rich riparian zone habitat on the numerous low river terraces formed by the Colorado River, with as many as 316 bird species, 79 plant species and 34 kinds of mammals.