More to explore:
Petroglyphs, Pictographs, Cave Paintings, Geoglyphs - Crystalinks
The mysterious holes of Sarisarinama, Venezuela
Stone foundation tablet with an inscription of Gudea, 2136-2121 BC, Lagash II, Mesopotamia Walters museum
McKee Rock Art, probably the most famous figure in Dinosaur National Monument.
Ancient Pueblo-Anasazi rock art of a warrior with a bear claw shield - New Mexico