Raiden Castle


Raidenjou (2).jpg


Raidenjō is thought to have been built by the Kosuge Clan, vassals of the Nishina Clan, to protect the easterly mountainous hinterlands of Nishina territory. The fort was also called 'Toriyajō'.

Visit Notes

Raidenjō is a yamajiro (mountaintop castle) ruin in Yasaka Township, Ômachi Municipality. The layout of the fort is fairly compact, but I found it interesting, and the remains were quite impressive. Features include dorui (earthen ramparts), horikiri (trenches), tatebori (climbing trenches) and kuruwa (baileys). Between the first and second bailey is a complex arrangement of embankments.

One pit formed from these ramparts is very deep. I think this was intended as a reservoir, storage pit or fire pit, rather than as a trap for enemies. The gently curving tatebori appear to have been carved or augmented from natural terrain to prevent enemies from moving laterally along the mountainside, and the central tatebori is very striking.

Raidenjō is surrounded by rugged and steep terrain, and would've been very difficult to assault. Having rented an electric bike from Shinan-Ômachi Station, I cycled up the steep mountain roads to reach the highest point along the road which ran just below the castle-mount. I was worried that if I were to descend along the road on the other side, I may not be able to find a way up to the castle, and I would have to start from the bottom or cycle back up the hill. However, it was fool-hardy of me to climb up the southern ridge, which is very dangerous, being basically a cliff made from a pile of boulders with loose rock and trees between.

Having made that daunting climb, I disturbed a goatelope on the ridge. It bounded off and then, from a safe position, glared at me in its idiot manner. King of mountain, ye, with mien of jester. Probably it had not been expecting the sudden appearance of a human from a cliff it couldn't climb itself. The idiot goat (a 'serow', but who knows what that is?) went bleeting off to its fellows down the mountain.

Since I didn't want to climb back down the way I had come, I followed a path from the east of the ridge to exit the site. It eventually disappeared, but I was able to get back down to the road not too far from where I had left my bike at the southern ridge terminus. It seems like cliffs go all around the mountain, but just around the sloping bend there is an old stairway which goes up through a creek with many large stone slabs which look like a cyclopean stairway.

And how! I probably could've got up there instead. Silly me. It's always worth checking for a safer way up the mountain... Yet, the castle-bloggers I was using for reference both gave up climbing to this medieval wreck, putting safety first. Wise of them. 'And if to live, the fewer men, the greater share of honour'.

  • Trench complex with 'rib' berm

Castle Profile
English Name Raiden Castle
Japanese Name 雷電城
Alternate Names Toriyajō
Founder Kosuge Clan
Year Founded Sengoku Period
Castle Type Mountaintop
Castle Condition Ruins only
Historical Period Pre Edo Period
Visitor Information
Access Shinano-Ômachi Station on the Ôito Line; rental e-bike
Visitor Information 24/7 free; mountain
Time Required 40 minutes
Location Ômachi, Nagano Prefecture
Coordinates 36° 29' 35.70" N, 137° 55' 36.19" E
Loading map...
Added to Jcastle 2023
Contributor ART
Admin Year Visited Viewer Contributed
Friends of JCastle
Shiro to Kosenjō

(one vote)
Add your comment welcomes all comments. If you do not want to be anonymous, register or log in. It is free.