Nakatsu Castle

Originally built in the 1580s by Kuroda Yoshitaka, one of the generals who helped unify Japan under Toyotomi Hideyoshi. Its location on the coast meant the original design incorporated saltwater into its defensive moat, an unusual feature still visible today. The current keep is a reconstruction from 1964, but the stone foundations, moat, and surrounding layout are original. Inside, a museum traces the castle's history and includes exhibits on Rangaku, the study of Western learning that flourished in Nakatsu during the Edo period. The city also has a connection to Fukuzawa Yukichi, the Meiji-era reformer whose face appears on the 10,000-yen note, and a museum dedicated to him is a short walk away.