How were Japan's ancient burial mounds made? This is a beginner's guide to what lies beneath the shape — the way the mound was built, the burial chamber inside, and the stone itself — with links to kofun you can actually visit.
A kofun's construction can be understood in three layers, from the outside in. The mound shape — filtered on the map — is the outermost layer; inside it are the building technique and the burial facility.
Large mounds were built as several stepped terraces — three tiers being standard — with haniwa lined along each waist. Japan's largest, Daisen Kofun (the Nintoku tomb), is a three-tiered mound.
A skin of stones covering the mound slopes. It prevented erosion and created a gleaming white appearance. Goshikizuka Kofun in Kobe — Japan's first fully reconstructed mound — lets you experience that original look with restored fukiishi and haniwa.
Rammed earth (hanchiku) is a layered, compacted foundation used in terminal-period octagonal mounds. The surrounding moat (about a quarter of the kofun on this map have one) and the projection (tsukuridashi) — a platform for ritual on the mound's side — are also key mound elements.
The interior changed dramatically over time. This evolution is the heart of kofun "construction."
| Type | Period | Character |
|---|---|---|
| Pit-style chamber | Early (3rd–4th c.) | Dug from above and sealed. No later burial. An individual chief's tomb. |
| Corridor-style chamber | Late Middle–Late (5th–6th c.) | Entrance passage + chamber. Reopenable for later burials; many can be entered today. |
| Corridor-slab chamber | Terminal (7th c.) | A small chamber hollowed from megaliths, finely cut. The age of cremation begins. |
The Early-period method: the coffin was placed and sealed with a ceiling stone. Sakurai-Chausuyama and Mesuriyama are representative. Shiga's Yukinoyama Kofun is famous for the 1989 discovery of an undisturbed pit-style chamber whose grave goods survived intact.
Spreading under influence from the Korean peninsula, this chamber could be entered from the side, allowing later burials and giving mounds a family-tomb character. Open chambers can still be entered today — the highlight of touring kofun.
By the 7th century, more enclosed and refined facilities appeared — the corridor-slab chamber hollowed from megaliths, and the brick-laid (sen-zumi) chamber. Asuka's Iwayama Kofun is the type-site of the finely cut ashlar chamber, and the Oni-no-Manaita & Setchin show the floor and lid stones of a chamber exposed to view. Hanayama-Nishizuka and Obitoke-Koganezuka are rare brick-laid chambers.
In this period, the tombs of sovereigns adopted the octagonal octagonal mound — Kengoshizuka, Nokuchi-no-Ohaka (the Tenmu-Jito joint mausoleum), and Nakaoyama (a candidate for Emperor Monmu's tomb).
The coffin itself changed too. From the Early-period split-log coffin, to the chest-shaped sarcophagus (Middle period, royal grade), and then the house-shaped sarcophagus (Late–Terminal). House-shaped types are either monolithic (hollowed from one stone) or composite (assembled from slabs).
Where the stone for a chamber or sarcophagus came from is a clue to the occupant's power. Tatsuyama stone from Hyogo and Nijozan tuff from Nara were favored for royal-grade sarcophagi in the Kinai region.
Most striking is Aso pink stone (welded tuff from the Uto Peninsula in Kumamoto). It was carried from Kyushu across the Inland Sea all the way to Lake Biwa, used in the house-shaped sarcophagi of Shiga's Kabutoyama and Maruyama kofun. Behind a single coffin lies a wide ancient network.
The "Iwase-type" chamber with stone shelves and beams, seen at Wakayama's Tennozuka Kofun and Kainan's Muroyama cluster, is a technique unique to Kii, using the local crystalline schist.