If you want something to last as long as possible, put it in stone.
Ancient cave art is fascinating. It is a glimpse into a mysterious world of transcendent shamanic vision that has been forgotten from Western culture for centuries. These resonant underground chambers were used to induce altered states of consciousness through graphic art, drumming, chanting and the possible use of ego-annihilating psychoactive substances.
On Neatorama, I saw a link to a seemingly anachronistic phenomenon: 19 -century Australian aboriginal cave paintings depicting European sailing & steam vessels. The article has a interesting slideshow with great photos.
In other Rock News, I came across a bunch of cool pictures of Sarah Palin's worst nightmare: An area in Bolivia full of petrified dinosaur footprints. Even crazier is the fact that the footprints go vertically up the rock. The ancient ground has been pushed up sideways over millions of years by the Earth's massive tectonic forces.
Of course, it is possible that the footprints are actually from devils running up & down the cliffs as their master, Satan was being tossed into the pit of fire by a pissed-off Yahweh.
You have to consider all options...