Isolated from development by a fortress-like bastion of thousand-foot-high cliffs of Wingate Sandstone, Sewemup Mesa is one of the most ecologically pristine areas in western Colorado. Since most of the mesa has never been grazed by livestock, it provides a rare example of an ecosystem largely undisturbed by human activity. These cliffs rise out of the slickrock gorge of the Dolores River on the east, and to the west they loom above Sinbad Valley, the remnant of a collapsed salt dome. Towering ponderosa pines line the canyons of the mesa top and grow directly from sandstone terraces along the mesa’s western cliffs. In contrast to the heights of Sewemup Mesa, adjacent Roc Creek Canyon plummets 1,000 feet straight down, its brilliant red walls framed by forests of Douglas fir and ponderosa pine.