Hirohata Shell Mound: A Late Jomon Site on Lake Kasumigaura
The Hirohata Shell Mound (広畑貝塚, Hirohata Kaizuka) is a Late to early Final Jomon settlement with a shell midden in Iide, Inashiki City, Ibaraki Prefecture, and was designated a national Historic Site in 1982.
According to the Agency for Cultural Affairs, the site lies on the southwest shore of Lake Kasumigaura, at the foot of hills bounded by the mouths of the Nodanagawa (Sakuragawa) River to the east and the Ono River to the west. The shell layers spread across low ground about 1.5 to 2.0 metres above sea level, and deposits containing artefacts continue into the rice fields to the north.
The Hirohata Shell Mound was designated on 27 February 1982. Ibaraki Prefecture's Board of Education gives the location as 635-1 Hirohata, Iide, Inashiki, and neighbouring lots.
Why It Is Protected: A Clue to Jomon Salt-Making
Since the Meiji era the site has been known for complete pots and many other finds. Before the war it was reported on by Emi Suiin, Kiyono Kenji and Ikegami Keisuke, and after the war Wajima Seiichi, Naora Nobuo, Yoshida Itaru and Kondo Yoshiro carried out excavations.
The finds range from a substantial group of later Late Jomon pottery to objects of the beginning of the Final Jomon. Especially striking are the large numbers of clay objects, such as figurines (dogu), clay tablets and ear ornaments, and of bone and antler work, such as shell bracelets, points, bone arrowheads and ornaments.
Both the national agency and the prefecture single out a group of thin, undecorated deep bowls from the end of the Late to the start of the Final Jomon. Hardened calcium carbonate clings to them and their walls flake away thinly, much like the salt-boiling vessels of the Kofun period and later. They are the basis for the theory that salt was already being made in the Jomon period, which makes the Hirohata Shell Mound important for understanding Jomon production.
What to Look For
Unusually, the shell layers here lie not on a hilltop but on low ground at the foot of the hills, about 2 metres above sea level. On site, compare the height of the hills behind with the flat fields in front, and picture how far the shores of Kasumigaura once reached.
The salt-making vessels make most sense in this setting. The idea is that people on the shore of a brackish inlet boiled seawater down in thin pots to produce salt.
The excavated objects appear to be held by various research institutions, and none can be seen at the site. Treat a visit as a chance to read the landscape rather than to see artefacts.
Visiting the Hirohata Shell Mound
The site is in Iide, Inashiki, near the southwest shore of Lake Kasumigaura. The surroundings are farmland and railway stations are far away, so a car is the practical option.
No official information on hours or fees could be found. The site appears to include rice fields and private land, so stay off farmland and private property and view it from roads and other public spaces.
There is no published restriction on photography, but avoid getting in the way of farm work. Enquiries go to the cultural properties section of Inashiki City.
Q&A
- What period is the Hirohata Shell Mound from?
- It is a settlement with a shell midden from the Late to early Final Jomon period.
- Why is the Hirohata Shell Mound a Historic Site?
- Besides abundant figurines and bone tools, it yielded thin deep bowls that may show Jomon salt-making, making it important for understanding Jomon production. It was designated in 1982.
- What are the salt-making vessels from the Hirohata Shell Mound?
- Thin, undecorated deep bowls with hardened calcium carbonate that resemble later salt-boiling pottery, suggesting that salt was made in the Jomon period.
- How do I get to the Hirohata Shell Mound?
- It is in Iide, Inashiki, far from railway stations, so a car is the practical choice.
- Can I see the finds at the Hirohata Shell Mound?
- No artefacts are displayed on site. A visit is about the location and landscape.
Basic Information
| Name | Hirohata Shell Mound |
|---|---|
| Location | 635-1 Hirohata, Iide, Inashiki City, Ibaraki Prefecture, and other lots |
| Designation | Historic Site |
| Year Designated | Designated 1982/02/27 (Showa 57) |
| Quantity | 1 site (shell midden and settlement) |
| Dimensions | Shell layers on low ground about 1.5 to 2.0 m above sea level |
| Owner | Not listed in the Agency for Cultural Affairs database |
| Public Access | Outdoor site. No official hours or fees published |
References
- Agency for Cultural Affairs, Database of National Cultural Properties: Hirohata Shell Mound
- https://kunishitei.bunka.go.jp/bsys/maindetails/401/448
- Cultural Heritage Online: Hirohata Shell Mound
- https://online.bunka.go.jp/heritages/detail/137844
- Ibaraki Prefectural Board of Education: Hirohata Shell Mound (Japanese)
- https://kyoiku.pref.ibaraki.jp/bunkazai/kuni-106/
Last verified: 2026.09.27