The landscape around Kansai, in southern-central Japan, especially around Osaka and Nara, is dotted by curious keyhole-shaped mounds surrounded by moats. These peculiar structures are ancient burial mounds called kofuns.

Kofuns were built by the Imperial family and members of the ruling classes as tombs for the noble, the elite and the powerful. 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. The distinctive keyhole shape appeared between the third and the early seventh centuries, and is characteristic of this period of Japanese history. Indeed, the period when kofun started appearing has been named the kofun period.

Daisen Kofun in Sakai. Photo credit: travel.rakuten.com

Kofuns have had various shapes throughout history, such as circles and squares, but the most common shape was that of a keyhole. According to Mr. Kurahashi, curator of the Sakai Museum, the shape is a symbol of power and authority. These kofuns are made up of two sections —a circular mound where the sarcophagus lies buried, and connected to it is a trapezoidal mound, where ceremonies and rituals were performed during the burial.

The burial chamber of kofuns consisted of a wooden coffin placed at the bottom of a shaft, which was then surrounded by walls made up of flat stones and sealed shut by a stone roof. 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.

One of the earliest keyhole-shaped kofun was built in the Makimuku area, in the southeastern part of the Nara Basin, in the middle of the 3rd century AD. Kofun making then spread to Yamato Province, and then to Kawachi, where gigantic burial mounds, such as Daisen Kofun of Emperor Nintoku exist.

Daisen Kofun and other smaller kofuns seen in this satellite photo of Sakai city.

Daisen Kofun, located in the outskirts of the ancient city of Sakai, in Osaka prefecture, southwest of Tokyo, is massive in size. Built in the middle of the 5th century, the kofun stands 35 meters tall and is 486 meters long, or twice as long as the base of the Great Pyramid in Giza. While it has only a quarter of the height of the Great Pyramid, the kofun supposedly has a much greater volume.

Just south of Daisen Kofun lies a much smaller kofun, belonging to Emperor Nintoku’s son, and to the east is the second largest tumulus, made for Emperor Ōjin, Nintoku's father. Around Nintoku’s tomb are 16 other smaller satellite tombs containing other members of the royal family including the empress and other female members of the royal family.

There are as many as 161,560 kofun tomb sites all over Japan. Many of these sites have long been reclaimed by nature, and appear like small hills covered by trees and vegetation. 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

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 Gyōda, Saitama. Photo credit: TY/Flickr

Kofuns in Saitama. Photo credit: yahoo.co.jp

Sources: Wikipedia / GMA News Online / Japan Reference