Along these trails one often encounters rock piles called cairns, which may represent trail markers or shrines where native peoples passing by hundreds of years ago, would toss a rock on the pile to thank the spirits for a safe journey. While most of the whole ollas left by Indians have been illegally collected by treasure hunters, fragments of pots can still be found scattered throughout the desert. These potsherds represent pots that were either dropped in place or perhaps stashed and later broken by the elements or by modern people. Look for these midden near water sources and areas protected from the sun and the wind. Rock Art Probably the most intriguing cultural resources in the park are the many examples of rock art.
Petroglyphs are designs and symbols etched into the surface of large boulders or rock faces.
This type of rock art is more common in the northern part of the park. Pictographs are painted or drawn on rock walls and are more common in the southern parts of the park. A specific type of petroglyph, sometimes called a yoni, is a natural crack in a large boulder which has been enhanced by stone tools to look like a human vulva. Yonis are believed to be associated with female fertility rites. Cupules look like tiny shallow mortars, approximately two centimeters across, and are found on vertical as well as horizontal rock surfaces.