Rock Art is most likely one of the oldest form of art, presented by human before developing writing or even speaking capabilities. Early samples of rock art are created by pecking stone tools on stone rocks.
Iran plateau as one of the oldest residencies of human being, is also hosting thousands of pieces of rock art, dating back to 40,000 years ago.
Standing in front of some thousands of years old engraving is kind of feeling which is not expressible; however I hope sharing the following photos could also share that feeling with you.
The photos are taken in Khomein Region, the land which seems its effect on Iran history is endless by introducing late Ayatollah Khomeini, as latest.

33° 52' 38.90" N 50° 4' 36.17" E