These peculiar structures are ancient burial mounds called kofuns.
They ranged in size from a few meters to over four hundred meters long.
The more powerful and influential the person was, the bigger his kofun is.
Indeed, the period when kofun started appearing has been named the kofun period.
Daisen Kofun in Sakai.
Finally, earth was mounded over the top.
Sometimes the surface of the tomb was paved with rocks.
The deceased was buried with several funerary goods such as bronze mirrors, weapons and armor.
Ornaments made of jade and jasper have also been discovered.
Daisen Kofun and other smaller kofuns seen in this satellite photo of Sakai city.
There are as many as 161,560 kofun tomb sites all over Japan.
Most of them have remained intact, as they are protected by law against archaeological excavations.
Only a handful of them have been excavated and explored.
A kofun in Okayama prefecture.
Photo credit:www.okayama-kanko.jp
The ancient Tannowa Nisanzai Kofun in the town of Misaki, Osaka Prefecture.
Photo credit:Japan Times
Fujinoki Tomb In Ikaruga, Nara Prefecture, Japan.
Photo credit:663highland/Wikimedia
Inside of Ishibutai Kofun in Asuka, Nara.
Photo credit:Purple X/Flickr
Inariyama Kofun, in Gyoda, Saitama.
Photo credit:TY/Flickr
Kofuns in Saitama.
Photo credit:yahoo.co.jp
Sources:Wikipedia/GMA News Online/Japan Reference
