National Treasures & Important Cultural Properties
of National Institutes for Cultural Heritage, Japan

　　The Tenjinyama Tumulus is part of the Yanagimoto Tumuli located to the east of the Yamato Basin and is a 113-meter-long, massive keyhole-shaped burial mound located to the west of the imperial mausoleum of Emperor Sujin. These bronze mirrors were found inside and outside of a wooden box in a pit-style stone chamber located at the center of the circle part. The box contained 41 kg of cinnabar surrounded by 20 mirrors placed with the mirror side facing upward and 3 mirrors were also placed outside the wooden box. Other items including an iron knife, an iron sword, iron arrowhead, a small knife and a hook were also found inside and outside of the box. The mirrors were placed clockwise along the wooden box from the north and 20 mirrors completed the circle. Outside of the box, 2 mirrors were placed in the north and one mirror was placed in the south. The details of the mirror types were as follows:

mirrors decorated on the back with square patterns and rulers and compasses design (hōkaku kiku mirrors): 6
mirrors decorated on the back with inward-facing petals design (naikō kamon mirrors): 4
pictorial-rimmed mirrors decorated on the back with gods and divine beasts design (gamontai shinjū mirrors): 4
mirrors decorated on the back with beasts design (jūkei mirrors): 4
mirrors decorated on the back with pictures of ancient China design (gazō mirrors): 2
triangular-rimmed mirrors decorated on the back with various gods and divine beasts design (sankakubuchi henkei shinjū mirrors): 2
a mirror decorated on the back with humans, birds and beasts design (jinbutsu chōjūmon mirror): 1

　　The age of the Tenjinyama Tumulus is thought to date from the late fourth century. However, these mirrors found in the tumulus are an unusual combination of mirrors, which does not include any of the sankakubuchi shinjū mirrors commonly found in tumulus of the early fourth century, but mainly includes hōkaku kiku mirrors and naikō kamon mirrors from the Eastern Han dynasty. Given that no buried human bodies were found in this tumulus, it may be a side burial mound (baichō) where only relics from the imperial mausoleum of Emperor Sujin were buried.