"They camped that night at the Hueco tanks, a group of natural stone cisterns in the desert."
East Mountain at Hueco Tanks State Park
Creative Commons AttributionEast Mountain at Hueco Tanks State Park - Credit: Brian Stansberry

The Hueco Tanks are a rocky outcropping in the middle of the desert near El Paso. Hueco means hollows in Spanish after the bowl like depressions in the rock which hold small pools of water formed by natural springs.