They consist of a group of three very large outcroppings of igneous rock that rise some 300 feet above the level desert plain. Each outcropping forms a small mountain of solid rock half a mile or more long and almost as wide, with no soil on its tops or sides, except in small hollows and crevices. Consequently only a few cedars, twisted, stunted oaks and other small vegetation grow on them. Very large boulders and large pieces of rock are on the mountains and piled around their base. In general the mountains slope up from the east side and end in high precipices on the west.
Deep canyons extend into the rock mass at several places.
The tanks referred to in the name are natural crevices in the rocks near the ground level which catch and hold rain water which falls on the rocks above. This water is sweet and cold and furnished the Indians and later the pioneer and now furnishes the ranchers with a generous supply of excellent drinking water in an otherwise arid desert the nearest natural water supply being the Rio Grande River thirty miles away. This group of pictures appears on a protected vertical rock wall overlooking the entrance to the main tank, and can easily be seen by everyone who visits the location. The top of the pictures are about 10 feet from the ground and must have required a ladder for their making. This group is perhaps the best example of a historical culture using white extensively, found at various sites at the tanks.