Bas-reliefs on the great staircase of Apadana Palace, Persepolis. Representatives of the various states bring tributes to the Persian king. The horses are the Caspians; a small horse breed native to Northern Iran much shorter than a regular horse but different from a pony. One of the oldest horse breeds in the world, very fast and strong that meet the Persian Empire requirment for fast message transport on a huge scale. Persepolis ia a 2500-year old World Heritage Site of ancient Persian palaces and temples. It was the ceremonial capital of the Persian Empire during the Achaemenid dynasty. At the height of its power, the Achaemenid Empire encompassed about 7.7 million square kilometers and spanned three continents, as far west as Libya to nearly all Middle East, and to Central Asia.