Karatsu Castle, which stands open onto Karatsu Bay, has a rare structure that the stonework is directly put up out of the sea water. It is a medium-size castle with the Honmaru (main castle) located on top of Mt. Manto, the Ninomaru (2nd castle) and the Sannomaru (3rd castle) in the west, and the outer structures in the south. In 1576, Hideyoshi Toyotomi allowed Hirotaka Terasawa to be the head of Karatsu Clan. However, he fought the Battle of Sekigahara on the eastern side (Ieyasu’s forces), and was rewarded with a dominion with 123,000 koku. In 1598, Hirotaka abandoned the original castle of Nagoya and built a new castle on top of Mt. Manto. In 1637, taking responsibility for the defeat of Shimabara rebellion, Terasawa’s lands were all confiscated by the Shogunate. Later on, several domain lords had been placed as the castellans of this castle, and the Ogasawara family finally occupied it until the castle was dismantled by the Meiji restoration. The buildings were demolished and the castle site was changed into Maizuru Park. Later in 1966, the donjon in the 5th floor 5 layers, gates and the watch tower were reconstructed. Seen from the bridge over the Matsuura River, those constructions with surrounding stonework and white walls look impressive.