A cluster of ancient burial mounds made with tiered structures

The Oya No. 1 burial mound is a square burial mound consisting of a 5-tiered structure that is unusual nationwide. It has a 3-tiered grave mound and a 2-tiered foundation in the front part.
Its size is such that it extends 22.7m east to west and 16.2m north to south and reaches a height of 8m.
The tomb is a horizontal stone chamber with two sleeves. A wooden coffin and a Sue pottery coffin were used for the burial.
Also, it was discovered that gilt bronze long swords with head ornaments and gilt bronze goods were saved from being stolen from the tomb.
This valuable cluster of ancient burial mounds was designated in 2008 (the 20th year of the Heisei era) as a national historic site.