Tatsuoka Castle is a remarkable historic site in Taguchi, Saku City, Nagano Prefecture. Built during the final years of the Edo period, it is famous for its unusual five-pointed star-shaped fortress design, known in Japanese as a goryokaku or bastion-style fortification.
Japan has only two surviving examples of this distinctive star-shaped fortress design: Tatsuoka Castle in Nagano and the much larger Goryokaku in Hakodate, Hokkaido. This makes Tatsuoka Castle an especially interesting destination for travelers interested in Japanese history, military architecture, and the dramatic transition from the Edo period to modern Japan.
The castle was associated with Matsudaira Norikata, lord of the Okudono Domain, later known as the Tatsuoka Domain. Construction began in the final years of the Edo period, and the principal buildings were completed in 1867, just as Japan was entering a period of enormous political and social change.
Strictly speaking, Tatsuoka Castle was not officially classified as a castle. It was a jinya, an administrative headquarters and residence for the domain lord, and was known as Tanoguchi Jinya. Nevertheless, its imposing star-shaped design has led to its popular names Tatsuoka Goryokaku and Kikyō Castle.
The Okudono Domain originally had its administrative headquarters in Okudono in Mikawa Province, in what is now the Okazaki area of Aichi Prefecture. However, much of the domain’s territory was actually located in Saku District of Shinano Province, present-day Nagano.
Matsudaira Norikata therefore requested permission from the shogunate to move the domain headquarters to Saku. During a period of growing political instability, establishing the administrative center closer to the domain’s main territories was considered important for effective and secure governance.
Matsudaira Norikata had a strong interest in Western military science. He designed Tatsuoka Castle based on the European bastion system, a style developed to withstand artillery attacks.
Construction progressed during the 1860s. The stone walls and earthworks were completed in 1866, followed by the main residential and administrative buildings in 1867.
The innovative design was unusual for Japan at the time, and local residents were reportedly allowed to visit and see the newly constructed facilities. The project reflects the growing awareness of Western military technology in Japan during the final years of the shogunate.
Although Tatsuoka Castle was designed as a star-shaped fortress, it was not a fully equipped modern military installation. The site covers approximately 20,075 tsubo, roughly half the area of Goryokaku in Hakodate.
Five projecting bastions form the distinctive star shape. At the center stood the main residence, while samurai quarters, a gunpowder storehouse, and religious buildings were arranged around it.
Interestingly, not every bastion had a gun emplacement. Only one cannon position was installed, at the southwest corner, while the surrounding moat was only about 7 to 9 meters wide.
These features limited its practical defensive capabilities. The design is therefore sometimes understood as reflecting Matsudaira Norikata’s strong intellectual interest in Western fortification techniques and the prestige associated with the new style, rather than being a completely functional modern fortress.
With the abolition of the feudal domains and establishment of prefectures in 1872, the Tatsuoka Domain was dissolved. Most of the castle buildings were subsequently dismantled and sold.
One important building, the former kitchen building, survived. It was moved to another location within the castle grounds and preserved. Today, it stands within the grounds of Taguchi Elementary School.
The site began being used for education in 1875, and the school remained an important part of the local community until it closed in 2022. The former school grounds now form part of the historic site where visitors can explore the remains of Tatsuoka Castle.
Although most of the original buildings have disappeared, several important elements of the fortress survive, including stone walls, the moat, and the former kitchen building.
The castle’s former grand hall was relocated to Jishoji Temple in Naruse, Saku City. The gate used as a secondary entrance was moved to Naritasan Yakushiji Temple in Nozawa. Another former castle gate was relocated to a private residence along the road leading toward Shinkai Sansha Shrine.
These relocated structures provide additional opportunities to trace the history of Tatsuoka Castle beyond the original site.
Tatsuoka Castle has been selected as Castle No. 129 on the Continued List of Japan’s Top 100 Castles. The former school grounds have been arranged as a historic site and can be explored freely.
Near the former main gate is the Goryokaku Deai-no-Yakata, where visitors can learn about the history and construction of Tatsuoka Castle through explanatory panels and historical materials.
For the best understanding of the fortress’s unusual design, climb to the viewpoint on the hill behind the castle site. From above, the five-pointed layout becomes much easier to appreciate than it is from ground level.
With permission from Saku City, aerial photography using a drone is also possible, offering a striking perspective of the complete star-shaped plan.
Tatsuoka Castle is a fascinating symbol of Japan’s final samurai era. Its construction came at a moment when the traditional feudal system was approaching its end and Japanese leaders were increasingly studying Western technology and military science.
Unlike traditional Japanese castles with tall keeps, elaborate gates, and massive stone walls, Tatsuoka Castle represents an experimental approach to defense inspired by European fortifications. Its unusual form makes it particularly valuable for understanding how Japan responded to rapid technological and political change in the 19th century.
Address: 3000-1 Taguchi, Saku City, Nagano Prefecture.
By car: Approximately 20 minutes from the Joshinetsu Expressway’s Saku-Minami Interchange, a distance of about 10 km.
By train: Approximately a 20-minute walk, about 1.5 km, from either Usuda Station or Tatsuokajo Station on the JR Koumi Line.
Note: There is currently no regular local bus service to the site.
Near Tatsuoka Castle is the Gozō Kawamura Memorial Museum, which introduces the works and life of sculptor Gozō Kawamura, who was born in the area.
Combining the castle ruins with the museum provides a broader look at the history and culture of Saku, from the dramatic final years of the samurai government to the artistic achievements of the modern era.
Tatsuoka Castle offers a rare chance to see a star-shaped fortress in a Japanese setting. Walking along its surviving moat and stone walls, then viewing the site from the nearby hill, allows visitors to appreciate both its distinctive geometry and its place in the turbulent history of 19th-century Japan.
For travelers exploring Saku, this unusual castle ruin is an especially rewarding stop for understanding the meeting point between traditional Japanese feudal culture and the new Western influences that emerged at the end of the Edo period.