Saga Castle

Saga Castle (formerly called Saga-jō or Saka-jō) is located in the heart of today’s Saga City. It was constructed in the early Edo period as the residence of the Nabeshima clan, lords of the Saga Domain. Its predecessor was Murauchi Castle, built by the Ryūzōji clan during the Sengoku period. During the Keichō era (1596–1615), it underwent large-scale expansion and renovation, eventually taking the form known today.

Unlike many famous Japanese castles characterized by massive stone walls, Saga Castle is distinctive for its earthen ramparts (dorui) and a broad moat more than 50 meters wide surrounding it. To conceal the castle’s interior, pine and camphor trees were planted atop the ramparts, making the fortress appear hidden within a forest. This earned it the nickname “Shizumi-jō” (the Sinking Castle). Its defensive system also incorporated water control: in the event of attack, water could be diverted from the Dobufuse River to flood all areas outside the honmaru (main bailey), turning them into a natural barrier.

However, comparison between the Keichō construction plans (Keichō Otsumi-ezu) and later maps of the castle town suggests that Saga Castle differed from its original design. For example, the number of yagura (turrets) was reduced, and the scale of stone walls around the honmaru and ninomaru was simplified. Scholars therefore regard Saga Castle as a “partially unfinished castle.”

During the Edo period, the castle town prospered thanks to the Nagasaki Highway (Nagasaki Kaidō), which connected Kokura and Nagasaki. The network of canals both inside and outside the castle served defensive and practical purposes, providing protection while also supplying daily water to townspeople.

In the Meiji period, Saga Castle suffered severe destruction during the Saga Rebellion (1874). The honmaru palace and most other structures were burned down, leaving only the Shachi-no-mon (Shachihoko Gate) and its adjoining turret, which survive today as Important Cultural Properties of Japan. The castle’s tenshu (main keep) had already been lost to fire during the Kyōhō era (1716–1736). Recent studies suggest that the original keep may have been similar in scale to, or even larger than, that of Kokura Castle.

Today, the remains of Saga Castle have been redeveloped as Saga Castle Park. The honmaru palace was reconstructed in wood in the 2000s and now serves as the Saga Castle History Museum, offering visitors insights into the history of the domain and local culture. Restored earthen walls and parts of the eastern moat give a sense of its former grandeur. The ninomaru area is now home to the prefectural offices, art museum, history museum, and schools, making the site once again the political, cultural, and administrative center of Saga Prefecture.