Akō Castle

Ako Castle (赤穗城, あこうじょう) is located in Ako City, Hyōgo Prefecture. During the Edo period, it served as the government headquarters and residence of the lords of the Ako Domain (also known as the Kariyano Domain). Today, the castle ruins are designated as a National Historic Site, while the Honmaru Garden and Ninomaru Garden are classified as Places of Scenic Beauty. Additionally, Ako Castle has been selected as one of the “Top 100 Japanese Castles” and the “Top 100 Historic Parks of Japan”, making it one of the most iconic landmarks of Ako.

The origins of Ako Castle can be traced back to Kakigami Castle, built in 1600 by Ikeda Nagamasa. Though later repaired under successive lords and governors of the Ikeda clan, it remained a relatively small fortress. In 1645, Asano Naganao became lord of Ako and petitioned the shogunate to construct a new castle. Construction began in 1648 and, after thirteen years, was completed in 1661, resulting in the Ako Castle seen today. Built in the peaceful post-war era of the Genna Armistice, its coastal location also made it notable as a seaside flatland castle.

The castle layout followed an irregular ring style: the honmaru (main bailey) was surrounded by the ninomaru, with the sannomaru stretching further north in a ladder-like arrangement. Designed with firearms warfare in mind, the castle incorporated numerous yagura (turrets), masugata (box-shaped gates), and defensive angles for crossfire. Interestingly, while the tenshudai (main keep foundation) was completed, a main keep (tenshu) was never built throughout the Edo period, with the stone base alone symbolizing the domain’s prestige.

Another unique feature was its water supply system. Due to the castle’s low elevation and brackish groundwater, the Ikeda clan established a sophisticated waterworks system, diverting clean water from the upper reaches of the Kumomi River through tunnels into the castle and castle town. This became one of Japan’s three great ancient waterworks systems.

Ako Castle is also famously linked to the Genroku Ako Incident (better known as the Chūshingura story of the 47 rōnin). Beyond this, several other disturbances occurred under different lords, such as the Shōhō Ako Incident under Ikeda Teruoki, the Wakisaka Ako Incident, and the Bunkyū Ako Incident during the Mori clan’s rule in the late Edo period.

Today, Ako Castle has undergone multiple restoration and reconstruction efforts, including the rebuilding of the Ōte Gate, Ōte Corner Turret, and the Ninomaru Garden. Excavations of the Honmaru Palace site have revealed the original garden and building layout. The area is now a park and a must-see spot for visitors and history enthusiasts, offering an immersive experience into the atmosphere of the legendary Chūshingura.