Jugoroana Cave Group

Jugoro-Ana Yokoana: A Cliff Face of 500 Ancient Tombs

On a wooded plateau in central Ibaraki, a soft tuff cliff has been honeycombed with the openings of more than 500 burial chambers. Archaeologists have confirmed 274 of them so far, and survey work suggests at least that many more lie hidden in the brush and beneath layers of fallen earth. Together they form Jugoro-Ana Yokoana, the largest cluster of cave tombs in eastern Japan and, since February 2024, a National Historic Site.

The site sits in the Nakane district of Hitachinaka City, on a tongue of high ground squeezed between the Okawa and Hongo rivers, both tributaries of the Naka. People began carving tombs into the cliffs here in the early seventh century, in the closing years of the Kofun period. They kept using the same chambers for additional burials right through to the early ninth century, deep into the Heian period. Few archaeological sites in the country trace such a long, unbroken thread of funerary practice.

Three sub-groups and a strange name

The cliff faces divide naturally into three sub-groups, each on a different shoulder of the plateau. Sashibu, on the northern edge, sits next to Toratsuka Kofun, a keyhole-shaped mound famous for its painted stone chamber. Tatedashi, the southern group, is unusual: no large kofun was ever built here, yet some of its cave tombs were given small earthen mounds of their own, as if borrowing the dignity of a chieftain's grave. Kasaya, on the western plateau, began later, after Kasaya Kofun No. 6 and around the time of Kofun No. 7.

The name Jugoro-Ana comes from a folk tale rather than a record. Local tradition holds that the Soga brothers — Juro and Goro, famous medieval avengers — hid in these caves before their final raid. The story is almost certainly a later embroidery; the tombs predate the Soga incident of 1193 by some five centuries. But the names stuck, fusing "Ju" from Juro and "Goro" from Goro, and the site has been known by them since at least the Edo period.

Why archaeologists fought for the designation

The 2024 listing was a long time coming. Part of the Tatedashi group, just 34 tombs covering 620 square metres, had been a prefectural historic site since 1940. The new national designation expands the protected zone to 56,781.9 square metres and brings all three sub-groups under a single legal umbrella. It is the third national historic site in Hitachinaka, after the Mawatari Haniwa Production Site (1969) and Toratsuka Kofun (1974).

What makes the cluster valuable to specialists is not just its size. The chamber profiles let researchers read social change over two centuries. In Sashibu, the earliest tombs are contemporary with Toratsuka Kofun itself, suggesting the cave-tomb groups and the elite kofun were dug by overlapping communities. In Tatedashi, no chieftain's mound presides over the cliff; the people buried here seem to have been organising themselves without that political reference point. Kasaya tells yet another story, with construction starting only after the local keyhole kofun tradition had matured. Three sub-groups, three patterns of how ordinary kin groups related to their local rulers in the long transition from Kofun-period Japan to the early provincial state.

What a visitor actually sees

The tuff that the tombs are cut from is a soft, pale volcanic rock, easy to carve and easy to weather. Standing at the base of the cliff, you can step close enough to look into individual chambers. Each one was made with three parts: a forecourt (zentei), a short passage (sendo) and a rectangular burial chamber (genshitsu) at the back, walls dressed almost flat by iron tools more than a thousand years ago.

Of the three sub-groups, only Sashibu is straightforward to visit. A maintained path leads through the woods from the Hitachinaka Archaeological Center past Toratsuka Kofun and down a slope; the cliff opens up suddenly at the bottom, with several dozen mouths gaping at eye level. The other two groups lie on private or unimproved land and are not set up for general access. Wear sturdy shoes, and avoid the day after rain — the soil along the path turns slick fast.

What the chambers gave up to archaeologists has gone elsewhere. The collection at the Archaeological Center, a five-minute walk away, includes a long sword fitted with bronze square-headed mountings, recovered in 1950 from Tatedashi Tomb No. 32 and now a city-designated cultural property. A separate group of 266 items from Tomb No. 35 in the same sub-group was designated together in 2017. A 2011 excavation produced swords, gilt-bronze blade fittings, iron arrowheads and Sue ware, later registered as Ibaraki Prefectural cultural property. Magatama beads, kiriko-dama beads and a rock-crystal bead also turned up across the various campaigns.

Around the site

The single best companion to Jugoro-Ana is Toratsuka Kofun, ten minutes' walk away through the same patch of woodland. It is a fifty-six-metre keyhole-shaped mound built in the early seventh century, and its sealed stone chamber is famously painted with red ochre — geometric patterns, weapons and saddle furniture done in iron oxide over a white undercoat. The chamber itself opens to the public only twice a year, in spring and autumn, but a full-size replica is permanently on view at the Hitachinaka Archaeological Center next door.

The Center is the practical base for any visit. Its standing exhibition runs from Paleolithic finds up through medieval Hitachinaka, with a thoughtful section on Jugoro-Ana that places the chamber forms and grave goods in their wider Kanto context. Admission is free, parking is shared with Toratsuka, and the staff can point you to the path. From Tokyo, the trip takes about ninety minutes by Joban Line to Katsuta, then a transfer onto the Hitachinaka Seaside Railway and a twenty-minute walk from Nakane Station.