Black Canyon of the Colorado the Nevada side of the canyon is the Sauna Cave. This cave was drilled by miners working on Hoover Dam while it was being constructed. It is a deep cave with calcium carbonate crystals on the walls. At the end of the cave is a hot spring, which causes temperatures in the cave to reach . One prominent canyon that splits from this canyon south of the Hoover Dam is Boy Scout Canyon. Boy Scout Canyon has water running through it that is warmed from a geothermal source. On the Arizona side of the river, there are several large hot
Steamboats of the Colorado River shared information about the conditions on the river above them. Robinson piloted the "Explorer" above the point reached by Johnson into the Black Canyon of the Colorado, where they struck a rock that damaged the boat, 40 miles above where Johnson reached. Ives named that rock "Explorer's Rock". While the "Explorer" was being repaired by his engineer, Ives, Robinson and the boat's mate, took their skiff over the next two days farther up the river exploring up through the Black Canyon and beyond to the vicinity of Fortification Rock. Next day, they went two miles farther to Las Vegas Wash,