Which river system ran parallel to royal road

From near Babylon, it is believed to have split into two routes, one traveling northeast then east through Ecbatana (in present-day Iran) and on along the Silk Road, the other continuing east through the future Persian capital Susa (in present-day Iran) and then southeast to Persepolis.

answer; /// the correct answer is evidence of the olmec civilization has been found in southern american in a hot steamy forest, archaeologists have found earthen artifacts at several sites that were evidence of the olmec civilization. these   artifacts were mounds,courtyards and pyramids build of stones, also on top of the mounds were many monuments made of stone, some of these stone structures are very large, they weigh as much as 44