Kofuns: The Japanese Keyhole Tombs That Archeologists Can’t Touch

Bigger than the pyramids and even more mysterious

The Daisen, which is the largest Kofun — Image from Osaka info

The largest ancient tomb is neither the Pyramid of Giza nor the Taj Mahar but a mysterious Japanese keyhole tomb, Daisen Kofun.

Kofuns are majestic architectural pieces that lie in the heart of Osaka, and the citizens of Japan do not even know their mysteries.

The archeology community has no clue what’s inside these tombs. But according to local legends, the tombs were a show of power by the great men of ancient Japan.

The Legend of The Kofun

The design of these majestic Japanese tombs is mind-blowing. According to Japanese legend, men built the kofun in the morning, and the gods took over at night.

Experts have counted over 20,000 kofuns scattered mainly across Osaka. They were built for royal burials from the third to the sixth century AD.

They vary in size from a few meters in length to the longest, measuring 486 meters in length and 36 meters in height. This giant structure is called the Daisen Kofun.

The Daisen Kofun is the largest known monument existing on earth, larger than the two pyramids of Giza combined. Legend says it belonged to Emperor Nintoku, the sixteenth emperor of Japan.

The Magnificence of the Daisen Kofun

According to Hiroshi Kaibe, this kofun took fifteen years and eight months of uninterrupted work. Even with the help of gods, it still required more than 2,000 workers for fifteen years to build such a mega-structure.

No one knows what’s exactly inside the Daisen Kofun. It is against the law to excavate many of these tombs. Smaller ones were subject to lite archeology work, but that’s it. For this reason, most kofuns have grown untouched forests and green vegetation on them.

According to Izumi Tachibana, the Daisen Kofun is attributed to Emperor Nintoku because it’s written in ancient texts that among five kings sleeps the Emperor Nintoku. Yet, many still debate on who exactly is buried in the Daisen.

The Keyhole Design and Decoration

Not all kofuns have a keyhole shape, but mostly all the big ones have a keyhole design. Noriyuki Shirakami explains that the original tomb design was a circular dome. Then they added exterior circular structures to the tomb.

One part of the covering circular structure had to connect with the land hence the rectangular part of the keyhole design. People could connect to the tomb through this corridor.

The outside of the tomb was designed with three levels that scaled upwards, as seen in the picture below.

A model of the Daisen Kofun — image from thekanert

There were artisanal clay figures called Haniwa placed around the surface of the three levels of the outside of the tomb. These figures represented motifs such as houses, armor, helmets, and large stone crocks.

Kofun historians estimated that 29,000 Haniwa figures were used to decorate the outside of the Daisen.


Archeologists can’t help themselves but wonder what’s inside these giant monuments. But the Japanese hold them sacred and won’t even allow public visits to the tombs. They insist the tombs remain undisturbed to honor those buried there.

With a new scanning technology that can’t harm the integrity of these kofuns, the world might finally know what’s inside them in the future. In July 2019, the Mozu Kofuns were added to the list of UNESCO World Heritage sites.