Rock painting is one of the oldest forms of expression by humankind and pre-humankind.  It's still done, albeit usually no longer on caves using natural pigments.  Souvenir shops are full of rocks proclaiming the tourist trap in question; on the other hand, some modern painters still do serious work on stones, or on natural and/or manmade stone surfaces.  Find here sites commercial, personal and academic pertaining to any facet of this art.  Pictured:  a painting on the wall of an early Christian catacomb (the Cubiculum of the Sheep) depicting Moses unlacing his sandals. then striking a rock to get water from it.