Overview of Iiyama Castle
A Castle Built on Natural Defenses
Iiyama Castle stood on a hill with the Chikuma River to the east and mountainous terrain to the west. Its location provided natural defensive advantages while also offering views over the surrounding landscape.
The exact date of its construction is unknown, but by the early 14th century it was already associated with the Izumi clan. The castle later came under the control of the Takanashi clan. During the turbulent Sengoku period, it was extensively rebuilt and strengthened as a frontline base for the powerful Uesugi clan.
The Seat of the Iiyama Domain
During the Edo period, Iiyama Castle became the administrative center of the Iiyama Domain. A succession of feudal lords governed the domain before the Honda clan eventually took control.
The Honda family ruled Iiyama for ten generations, continuing until the end of the feudal system in the 19th century.
History of Iiyama Castle
The Castle During the Sengoku Period
In 1557, the invading forces of the Takeda clan drove Takanashi Masayori from his original residence, and he moved to Iiyama Castle.
In 1564, Uesugi Kenshin, the powerful warlord of Echigo Province, undertook a major reconstruction of Iiyama Castle as a strategic defensive base against Takeda Shingen of Kai Province.
This reconstruction is particularly significant because Iiyama Castle is regarded as one of the relatively few castles whose development was directly undertaken by Kenshin himself. Its position near the border between Echigo and northern Shinano made it an important part of the Uesugi defense network.
Changing Lords in the Late 16th and Early 17th Centuries
In 1578, Iiyama Castle was transferred to Takeda Katsuyori. Following the downfall of the Takeda clan, however, the castle changed hands repeatedly.
Its successive rulers included Mori Nagayoshi, Uesugi Kagekatsu, Ishikawa Mitsuyoshi, and Seki Kazumasa. Eventually, Minakawa Hiroteru, a retainer of Matsudaira Tadateru, entered the castle as its lord.
Minakawa later reported Tadateru’s misconduct to Tokugawa Ieyasu. As a result, he was removed from his position. The castle subsequently passed through the hands of several families, including the Hori, Sakuma, Sakurai-Matsudaira, Nagai, and Aoyama clans.
The Honda Clan and the Iiyama War
In 1717, Honda Sukeyoshi was transferred to Iiyama from the Ioto Domain in Echigo. From this point onward, the Honda family ruled Iiyama for ten generations.
The final chapter of the castle’s history came during the Iiyama War in 1868, part of the wider Boshin War that accompanied the collapse of the Tokugawa shogunate. The castle and surrounding town were attacked by forces supporting the former shogunate, and much of the castle town was destroyed by fire.
Following the abolition of the feudal domains and establishment of prefectures in the early Meiji period, Iiyama Castle was dismantled. Most of its original buildings disappeared, leaving only fragments of the former castle complex.
The Layout and Remains of Iiyama Castle
Honmaru, Ninomaru, and Sannomaru
The castle was arranged along a hill from north to south, with the Honmaru, or main enclosure, the Ninomaru, or second enclosure, and the Sannomaru, or third enclosure.
The West Enclosure was located at the foot of the western slope, while an outer enclosure extended to the north. A single line of moats surrounded the castle.
The Honmaru contained the lord’s residence, while the Ninomaru served as an administrative center. Turrets stood in the Sannomaru. The castle had approximately 12 gates, but it did not have a conventional main keep. Instead, a two-story turret served a similar defensive and symbolic function.
Stone Walls and Earthworks
The residences of senior retainers were concentrated mainly in the West Enclosure. Many of the castle’s stone walls collapsed during the Zenkoji Earthquake of 1847, but they were rebuilt in 1849.
Today, sections of stone walls and earthen ramparts remain, providing visible clues to the structure of the former castle.
Iiyama Castle Ruins Today
A Historic Park and Shrine
The former Honmaru is now occupied by the grounds of Aoi Shrine, while the former Ninomaru has been developed as a castle ruins park.
Walking around the site offers an opportunity to imagine the original castle rising above the surrounding town and river landscape. In spring, cherry blossoms fill the grounds with color, making the historic site especially attractive for a leisurely seasonal visit.
Relocated Castle Gates
Some architectural remains from Iiyama Castle survived because they were relocated to nearby buildings after the castle was dismantled.
A two-story castle gate, relocated from a private residence, remains near the former South Middle Gate site. Another gate known as the Fujimen Gate was moved to Myosenji Temple in Iiyama, while a gate believed to have been the rear gate was relocated to a private residence in Tago, Nagano City.
An unidentified castle gate was also moved to a private residence in Ebe, Nakano City. At Shinsoji Temple in Nagano City, a surviving structure identified as the former main gate remains, although its upper two-story section was lost to fire.
Exhibits About the Castle
Learning About Uesugi Kenshin and the Castle’s History
Panels commemorating the 450th anniversary of the construction work associated with Uesugi Kenshin are displayed at the Iiyama Castle ruins.
The exhibits include bird’s-eye views and a reproduction of the historic Iiyama Castle plan, along with explanations of the castle’s layout and defensive structures. Information concerning future plans for preserving and improving the historic site is also presented.
Visiting Iiyama Castle
Convenient Access by Train
Iiyama Castle ruins are conveniently located for visitors traveling by public transportation. The site is approximately a 5-minute walk from Kita-Iiyama Station on the JR Iiyama Line.
Access by Car
By car, take the Joshin-Etsu Expressway to Toyota-Iiyama Interchange and continue via National Route 117. Free parking is available at the Shiroyama Park parking lot, with space for approximately 20 vehicles.
Experience the History of Northern Shinano
Iiyama Castle witnessed centuries of political and military change, passing through the hands of numerous powerful families from the Sengoku period through the Edo period and remaining an important center of regional administration until the end of the feudal era.
Although the original castle buildings have disappeared, the remaining stone walls, earthworks, historic surroundings, and relocated gates preserve fragments of its past. The site also offers a peaceful setting where visitors can enjoy the changing seasons, particularly the beautiful cherry blossoms of spring.
For travelers interested in Japanese castle history, the Sengoku period, Uesugi Kenshin, and the traditional landscapes of northern Nagano, Iiyama Castle is a rewarding place to explore. Walking through the castle ruins while looking toward the Chikuma River provides a vivid sense of how geography and history shaped this important stronghold.