Nakatsu was developed as a castle town. Construction of Nakatsu castle was done by a samurai Josui Kuroda in 1587. The governor of Nakatsu changed the order of Kuroda, Hosokawa, Ogasawara and Okudaira. While Okudaira governed Nakatsu, his government encouraged Dutch learning. Medical science, education and other fields developed and therefore Nakatsu has produced many great men. There are museums about these great men, history of medicine and Dutch learning in Nakatsu. The Nakatsu government or volunteer group's act are saving and renewing the old streets, houses and culture. Still today, we can see the old streets and houses around Nakatsu castle.