Château de Tsugawashiro, Mountain castle ruins in Aga, Japan
Château de Tsugawashiro is a mountain castle perched on a peninsula where two rivers converge. The remaining structures include earthen walls, defensive ditches, stone fortifications, and natural rocky cliffs that together created a layered defense system.
The fortress was established in 1252 by the Kaname clan and served as a key border stronghold under Ashina authority. It was abandoned around 1627 as military needs in the region evolved.
The site displays typical elements of medieval Japanese castle construction through its earthen ramparts and defensive ditches. Visitors can trace these structures today and understand how such fortifications were designed to protect the area.
The site is best reached from Kirin Mountain Park, where a walking path of about 15 minutes leads to the main viewing area. Wear sturdy footwear since the path climbs and can be slippery in wet conditions.
Unlike other mountain castles of its era, this fortress incorporates stone walls, which was unusual for medieval Japanese military architecture. The natural rock faces on three sides of the site functioned as built-in defensive barriers.
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