During the Tumulus period, when emperors were called "Great Kings" ("okimi" in Japanese) in the Yamato kingdom, an emperor's tumulus was built in a circular shape with a rectangular frontage (from the tumulus of Kaika, the ninth emperor to that of Bidatsu, the thirtieth emperor).
天皇が大王(ヤマト王権)（おおきみ）と呼ばれていた古墳時代には、その陵は巨大な前方後円墳であった（9代開化陵～30代敏達陵）。