During the Kofun period, powerful priest kings and rulers emerged and eventually a nation state was forged. Tens of thousands of these burial mounds, particularly keyhole shaped mounds were erected, probably as a symbol of the power and authority of the rulers and kings. are surrounded by rice fields — the view probably looked similar in ancient times. … Click on the Tabblo> for a photo essay of a field trip to the Sakitama Burial Mounds in Saitama Prefecture.