Kofun period: the age of keyhole tombs

The period is named after the kofun, “old mounds”, raised over the graves of the elite from the mid-3rd to the early 7th century: more than 160,000 kofun sites are known, about 5,000 of them keyhole-shaped. This most characteristic type, the zenpō-kōen-fun, is square in front and round behind, so that from above it looks like a keyhole; clay offerings, haniwa, were set in rings on and around the mounds. One of the first large keyhole tombs is the Hashihaka Kofun at Makimuku in the southeastern Nara basin, about 278 m long. Its date is disputed — from the mid-3rd to the early 4th century, and some put it later still — and some scholars see in it the tomb of Queen Himiko, who died soon after 247; the Imperial Household Agency attributes it to the legendary princess Yamato-totohi-momoso-hime.

The concentration of the greatest mounds first in the Nara basin and then in Kawachi — the largest of all, the Daisen Kofun at Sakai, traditionally the tomb of Emperor Nintoku, is 486 m long and was built in the mid-5th century — is taken as evidence of a relatively centralised power, perhaps the origin of the Yamato polity and of the imperial line; in the 5th century keyhole tombs spread across the archipelago. Authors start the period around 250 or around 300; its end is conventionally set at 538, when Buddhism reached Japan and the Asuka period began, although keyhole mounds were built until the late 6th century.