Château de koi, Mountain fortress in Nishi-ku, Hiroshima, Japan
Château de Koi is a mountain fortress located on Chakusuyama with a primary court and secondary enclosures surrounded by moats and defensive earthworks. These fortifications follow the natural contours of the mountain to create layered defensive zones.
The fortress developed as a strategic stronghold in a region marked by frequent conflict and was built to withstand assault. In 1515, Takeda Motoshige launched an extended siege attempt that ultimately failed to penetrate its defensive systems.
The castle demonstrates how Japanese fortress builders worked with natural mountain features to create defensive spaces that felt integrated with the landscape. These design choices reveal how people in that era thought about protection and the relationship between structures and terrain.
The easiest access is from the Fujihaiutsu Fire Station bus stop, where a marked hiking trail leads to the fortress entrance. Guide ropes are installed along the path to help navigate the uneven mountain terrain.
The mountainside displays exposed bedrock at several points along the paths, which reveals the natural defensive advantages of this location. These rock formations show why the fortress builders selected this specific mountain and how they used the geology to reinforce their defenses.
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