Okō Castle, Medieval castle site in Nankoku, Japan
Okō Castle is a medieval castle site on the 97-meter-high Mount Oko above the Kokyo River valley in Nankoku. Stone walls, moats, and other fortifications spread across the grounds and show the original layout of the defensive complex.
The castle was built between the 13th and 14th centuries as the main fortress of the Chosokabe clan. It remained militarily important until the family surrendered to Hideyoshi Toyotomi in 1585.
The name comes from Mount Oko, which shaped this area for centuries and set the stage for the fortress. Today the grounds still show the layout of defensive works that once defined daily life for guards and residents.
Detailed maps of the castle layout are available at the local museum and help locate the remaining fortifications across the site. A walk leads through different levels, so sturdy footwear and enough time for the climb are advisable.
Several vertical moats and defensive trenches run through the grounds and become especially clear in winter when leaves fall. This design was rare in the region and aimed to stop attackers from several directions at once.
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