Nakatsu Castle

Nakatsu, Japan, Japan

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Nakatsu Castle in Nakatsu, Ōita Prefecture, is a historic water castle famously known as one of Japan’s three “castles on the sea” (mizujiro), along with Takamatsu Castle in Shikogo and Imabari Castle in Ehime, because its defensive moats were filled with seawater from the nearby Seto Inland Sea.

Originally built in 1587–1588 by the strategist Kuroda Yoshitaka (Kuroda Kanbei), a close ally of Toyotomi Hideyoshi, the castle served as the seat of power for several ruling clans over the Edo period, including the Kuroda, Hosokawa, Ogasawara, and finally the Okudaira families, until the feudal system was abolished in 1871.

The original castle was largely destroyed in 1877 during the Satsuma Rebellion and later abandoned, and the current three-story main tower (tenshu) was reconstructed in 1964 using Hagi Castle’s design as a reference, since the original shape was unknown, and it now houses a historical museum displaying swords, armor, and documents related to the castle and its lords.

Today, visitors can freely walk the castle grounds, enter the reconstructed keep for a museum and panoramic views of Nakatsu city and the surrounding mountains, and appreciate the fan-shaped layout of the castle with its stone walls and seawater moats, making it both an accessible example of a coastal castle town and a notable site for those interested in Japanese military history and Kyushu’s regional heritage.