An Ancient Mountain Fortress on Mount Raizan
The Raizan Kogoishi (雷山神籠石) is the remains of an ancient kogoishi-type mountain fortress on the slopes of Mount Raizan in Itoshima City, Fukuoka Prefecture, which in 1932 were designated a Historic Site.
The Agency for Cultural Affairs records lines of stones and sluices across the valley in a basin on the slopes of Raizan.
Itoshima City notes that excavations and an entry in the Nihon Shoki for 658 point most strongly to the mid-seventh century for such fortresses, and that Raizan was probably built then too.
Stone Lines and Sluices
According to the designation text, lines of stones run across the stream at two points in a basin on the slopes of Raizan, about 103 ken long upstream and 43 ken downstream.
Downstream, two sluices at different heights regulated the outflow; the upstream sluice had already collapsed, leaving only traces.
Itoshima City describes the north sluice as a solid structure of dressed stone 12 metres long, 10 metres wide and 3 metres high, with lines of stones climbing the steep slopes to the ridges from both ends. The south sluice has two kinds of outlet: a culvert beneath the stone line and a water channel through the wall.
What to Look For
Itoshima City explains that the name kogoishi arose because such stone lines, as at Mount Kora, were once thought to mark sacred precincts. Earth ramparts and palisade traces found at Otsuboyama in Saga, and parallels with ancient Korean fortresses, later showed them to be mountain fortresses; a dozen or more are known in western Japan.
The tall dressed-stone north sluice and the stone lines climbing the slopes convey the scale of the fortress.
Visiting the Raizan Kogoishi
No official visitor information could be found. The remains are in the mountains, so watch your footing.
Enquiries: Itoshima City cultural properties section, 092-332-2093.
Q&A
- When was it designated?
- On 25 March 1932.
- What is a kogoishi?
- The remains of an ancient mountain fortress of stone lines and sluices, probably mid-seventh century.
- How big is the north sluice?
- 12 metres long, 10 metres wide and 3 metres high, according to Itoshima City.
- Where does the name come from?
- Stone lines were once thought to mark sacred precincts.
- How is 雷山神籠石 read?
- Raizan Kogoishi.
Basic Information
| Name | Raizan Kogoishi (雷山神籠石) |
|---|---|
| Location | Raizan and Iihara, Itoshima City, Fukuoka Prefecture |
| Designation | Historic Site |
| Year Designated | Designated 1932/3/25 (Showa 7) |
| Quantity | Not recorded in the Agency for Cultural Affairs database |
| Dimensions | North sluice 12 by 10 metres, 3 metres high (Itoshima City) |
| Owner | Not recorded in the Agency for Cultural Affairs database |
| Public Access | No official visitor information found |
References
- Agency for Cultural Affairs Database: Raizan Kogoishi (Japanese)
- https://kunishitei.bunka.go.jp/bsys/maindetails/401/2621
- Cultural Heritage Online: Raizan Kogoishi (Japanese)
- https://online.bunka.go.jp/heritages/detail/173225
- Itoshima City: Raizan Kogoishi (Japanese)
- https://www.city.itoshima.lg.jp/s033/010/020/010/110/120/raizan-kougoishi.html
Last verified: 2026.09.28