Kawachi Province
Yao was in Kawachi Province, and considered in Kawachi Bay. This area was a fertile delta along Old-Yamato River, and has been cultivated since Yayoi period(from 200 BCE to 300 CE). In the Kofun Period(from 250 to 538), many powerful families settled here and many Kofuns(mausoleums) were constructed on the foot of Ikoma mountain range, and many of them remain until now.