Kagamiyama Castle (Hiroshima Prefecture) Complete Guide | History, Highlights, and Access Information for this National Historic Site Mountain Castle
What is Kagamiyama Castle?
Kagamiyama Castle is a large-scale mountain castle site representative of the Sengoku period, located on Mount Kagamiyama in Higashihiroshima City, Hiroshima Prefecture. Built around the summit of Mount Kagamiyama, which is 335 meters above sea level, the castle is located almost in the center of the Saijo Basin and played an important role as a strategic point in Aki Province (present-day western Hiroshima Prefecture).
Also known as “Saijo Castle” and “Kagami Castle,” it was designated a National Historic Site in 1998. Currently, it is maintained as Kagamiyama Park, and the castle remains such as baileys, moats, vertical trenches, stone walls, and well remains are well preserved.
Geographical Characteristics of Kagamiyama Castle
Mount Kagamiyama, where Kagamiyama Castle was built, is an isolated peak overlooking the Saijo Basin. Its elevation is 335 meters, and its relative height (height from the base) is approximately 100 meters. This location was militarily excellent, making it an ideal base for monitoring and controlling the surrounding roads.
From the mountaintop, one can see not only the city of Higashihiroshima but, on clear days, even the Seto Inland Sea, allowing one to imagine the view the castle lords of the time had as they surveyed their territory.
History of Kagamiyama Castle
Construction Period and Background
There are various theories regarding the construction period of Kagamiyama Castle, but archaeological excavations suggest that the first castle was built around the Nanboku-cho period (mid-14th century). Historical documents indicate that it was extensively developed by the Ouchi clan around the Chōroku-Kanshō era (1457-1466).
At that time, Aki Province was a region divided among several local lords, but the Ouchi clan, a powerful daimyo based in Suō Province (present-day Yamaguchi Prefecture), was expanding its power and strengthening its influence in Aki Province. Kagamiyama Castle was one of the castles that the Ouchi clan considered important as a base for their control of Aki Province.
The Ouchi Clan’s Rule of Aki Province and Kagamiyama Castle
The Ouchi clan was a powerful daimyo family that ruled the western part of the Chugoku region from the Muromachi period to the Sengoku period. Kagamiyama Castle was staffed by senior retainers of the Ouchi clan as castle lords, and it functioned as an important base supporting the Ouchi clan’s power base in Aki Province.
Records show that names such as Kurata Fusanobu served as castle lord. The Kurata clan was known as a hereditary vassal of the Ouchi clan and was entrusted with the defense of Kagamiyama Castle and the governance of the surrounding area.
Conflict with the Amago Clan
At the start of the Sengoku period, the Amago clan, based in Izumo Province (present-day Shimane Prefecture), expanded its power and attempted to advance into Aki Province. Kagamiyama Castle, an important stronghold of the Ouchi clan, was an obstacle to the Amago clan’s conquest of Aki Province.
For this reason, Kagamiyama Castle was frequently attacked by the Amago clan. Located on the front lines of the power struggle between the Amago and Ouchi clans, Kagamiyama Castle became a stage for the turmoil of the Sengoku period.
The Battle of Kagamiyama Castle (Daiei 3, 1523)
The most important event in the history of Kagamiyama Castle is the “Battle of Kagamiyama Castle,” which took place in Daiei 3 (1523). This battle is known as the battle that marked the emergence of Mori Motonari, who would later become the ruler of the Chugoku region, onto the historical stage.
Against the Amago clan’s invasion, Mori Motonari, then a young local lord, fought on the side of the Ouchi clan. It is said that Motonari used skillful tactics to outmaneuver the Amago army and successfully defended Kagamiyama Castle. This achievement earned Motonari the trust of the Ouchi clan, laying the foundation for his later rise to power.
Abandonment and Aftermath
Kagamiyama Castle is believed to have been abandoned around Daiei 5 (1525). Subsequently, the Ouchi clan’s base of operations in Aki Province was moved to another castle. However, the castle ruins have been preserved in relatively good condition over the long years, and to this day remain a valuable historical site that conveys the appearance of a mountain castle from the Sengoku period.
Structure and Layout of Kagami-yama Castle
Characteristics of a Concentric Mountain Castle
Kagami-yama Castle is classified as a concentric mountain castle. A concentric castle is a construction method in which multiple enclosures (flat areas) are arranged in a continuous line along the mountain ridge. At Kagami-yama Castle, large and small enclosures are arranged in a stepped fashion along the ridge, centered around the main enclosure at the mountaintop.
This structure had the advantage of allowing for gradual defense at each enclosure when an enemy attacked. Furthermore, it is a defensive design that makes maximum use of the unique terrain of a mountain castle.
Major Enclosure Groups
More than 10 enclosures of varying sizes have been identified at Kagami-yama Castle. The main enclosure (honmaru), located at the mountaintop, is the largest flat area and is thought to have housed the lord’s residence and important facilities.
Surrounding the main enclosure are the second and third enclosures, each demarcated by earthworks and steep cliffs. Each enclosure is presumed to have been used as a lookout post, soldiers’ quarters, or armory.
Remains of Defensive Structures
At the Kagami-yama Castle ruins, various defensive structures characteristic of mountain castles from the Sengoku period can be observed.
Horikiri (Dry Moat): A large dry moat dug to cut across the ridge. An important defensive structure to prevent enemy intrusion, several horikiri remain at Kagami-yama Castle. Some reach depths of over 5 meters, demonstrating the advanced castle-building techniques of the time.
Tatebori (Vertical Moat): A dry moat dug vertically along the slope. These structures served to prevent enemy soldiers from climbing the slopes and to restrict their lateral movement. At Kagamiyama Castle, vertical moats were positioned on both sides of the main approach routes, demonstrating a strategy to limit the movement of attackers.
Kirigishi (cliffs): These are steep cliffs artificially carved out. They were constructed between or around enclosures, forming nearly vertical slopes 3-5 meters high. This made enemy intrusion difficult.
Dorui (earthen ramparts): These are defensive walls made by piling up earth. Built around enclosures and in important locations, they served to protect against arrows and firearms, and also provided cover.
Remains of Stone Walls
Remains of stone walls have also been confirmed at Kagamiyama Castle. While the use of stone walls was limited in mountain castles during the early Sengoku period, stone masonry was used in important areas at Kagamiyama Castle.
The existing stone walls were built using an old construction method called “nozurazumi,” where natural stones were stacked almost as they were. Although some sections have collapsed, it remains a valuable historical site for understanding the stone-laying techniques of the time.
Well Site
Securing water was a matter of life and death for mountain castles. At Kagami-yama Castle, the site of a well has been confirmed near the summit, suggesting it played a crucial role as a water source during sieges. The ability to obtain water at the summit significantly enhanced the castle’s defensive capabilities.
Highlights of Kagami-yama Castle
View from the Main Enclosure
One of the greatest highlights of Kagami-yama Castle is the magnificent view from the main enclosure. From the 335-meter-high summit, a 360-degree panorama unfolds, offering views of Higashihiroshima city, the Saijo Basin, and even the Seto Inland Sea in the distance.
During the Sengoku period, castle lords surveyed their territories from this location and monitored enemy movements. Currently, visitors can enjoy the beautiful scenery of each season, from cherry blossoms in spring to autumn leaves, making it a popular spot for tourists and hikers.
Well-Preserved Enclosures
At Kagami-yama Castle ruins, the layout of the enclosures from nearly 500 years ago is remarkably well-preserved. The flat surfaces of each enclosure, the cliffs separating them, and the surrounding earthworks are clearly visible, allowing visitors to experience the structure of a mountain castle from the Sengoku period.
The enclosures around the main keep are particularly large, giving a real sense of the castle’s grandeur at the time. Walking along the well-maintained paths and visiting each enclosure will help you understand the overall layout of the castle.
Moats and Vertical Moats
Among the defensive structures of Kagami-yama Castle, the large-scale moats are particularly impressive. These deeply excavated moats still maintain a depth of over 5 meters, attesting to the castle’s high level of defense at the time.
Vertical moats can also be found in multiple locations, and their sheer size is astonishing when climbing the slopes. These remains serve as evidence of the castle-building techniques of the Sengoku period and the immense effort invested in constructing this castle.
Stone Wall Remains
Although only partially intact, the surviving stone walls are also a highlight. While the rough-hewn stone walls lack the orderly beauty of later castles, they convey the simple techniques and strength of the Sengoku period.
The scattered remains of collapsed stones suggest that the stone walls once covered a much wider area.
Ascent Routes and Information Boards
The Kagami-yama Castle ruins are now maintained as Kagami-yama Park, with multiple ascent routes (hiking trails). Information boards and explanatory signs are installed along the main routes, allowing visitors to learn about the castle’s history and remains as they ascend.
Multiple ascent routes are available, varying in difficulty, allowing you to choose according to your fitness level and available time. Using the well-maintained paths, even beginners can reach the summit relatively safely.
Access to Kagamiyama Castle
Access by Public Transportation
Using the JR Sanyo Main Line
- Get off at Saijo Station on the JR Sanyo Main Line
- Take a bus from the station for approximately 10 minutes, get off at Kagamiyama Park Entrance, and walk for approximately 20 minutes to reach the trailhead.
- Alternatively, if walking from Saijo Station, it takes approximately 30-40 minutes to reach the trailhead.
Saijo Station is not a Shinkansen (bullet train) stop, but it is approximately 35 minutes from Hiroshima Station by conventional train and approximately 20 minutes by bus from Higashi-Hiroshima Station on the Sanyo Shinkansen.
Access by Car
Using the Sanyo Expressway
- Approximately 15 minutes by car from Saijo IC on the Sanyo Expressway
- Kagamiyama Park parking lot (free) is available.
The trailhead is a few minutes’ walk from the parking lot. The parking lot is divided into several areas, with a total of several dozen spaces. However, it can get crowded during peak tourist seasons such as cherry blossom season, so early arrival is recommended.
Address and Contact Information
Location: 739-0046 Kagamiyama, Higashihiroshima City, Hiroshima Prefecture
Contact Information:
- Higashihiroshima City Board of Education, Lifelong Learning Department, Culture Division
- Phone: 082-420-0977
Time Required for Climbing
From the trailhead to the main enclosure at the summit, using a typical hiking trail, it takes approximately 20-30 minutes one way. Including time for sightseeing at the summit, it’s advisable to allow 1.5-2 hours round trip.
If you plan to carefully examine the various remains or enjoy taking photographs, it is recommended to allocate more time.
Precautions for Climbing
Clothing and Equipment
Kagamiyama Castle is a full-fledged mountain castle, and preparation for mountain climbing is necessary for climbing.
- Shoes: Athletic shoes or trekking shoes are essential. Avoid sandals or high heels.
- Attire: Choose comfortable clothing and take appropriate precautions against cold or heat depending on the season.
- Items to Bring: Bring drinking water, a towel, a hat, and insect repellent (in summer).
- In Rainy Weather: The hiking trails can become slippery, so it is recommended to avoid climbing during rainy weather or immediately after rain.
Safety Precautions
- There are many steep terrains such as moats and cliffs, so please watch your step.
- Do not climb on stone walls or earthworks. For the protection of the remains and for safety, do not enter areas where ropes or fences are installed.
- It is recommended to climb in groups rather than alone.
- Cell phone reception may be unstable in some areas.
Visitor Etiquette
Kagami-yama Castle Ruins are a valuable cultural property designated as a national historic site. Please observe the following etiquette when visiting.
- Please take all your trash with you. – Please do not damage the ruins or move any stones.
- Collecting plants or capturing animals is prohibited.
- The use of fire is strictly prohibited.
Nearby Tourist Attractions
Saijo Sake Brewery Street
Around JR Saijo Station, there is an area called “Saijo Sake Brewery Street” where many sake breweries are located. The Saijo district of Higashihiroshima City is known as one of Japan’s three major sake-producing regions, alongside Nada in Hyogo Prefecture and Fushimi in Kyoto Prefecture.
You can enjoy sake brewery tours and tastings while strolling through the charming streets lined with sake breweries featuring red-tiled chimneys and white walls. It’s an ideal spot to visit in conjunction with a visit to Kagamiyama Castle.
Higashihiroshima City Museum of Art
This museum, which mainly exhibits contemporary art, serves as a hub for local culture and art. Regular special exhibitions are also held, allowing visitors to enjoy art appreciation.
Hiroshima University
Higashihiroshima City is home to the main campus of Hiroshima University, which includes facilities such as museums and botanical gardens within its vast campus. You can learn about Higashihiroshima City’s aspect as an academic city.
Points to Enjoy Kagamiyama Castle
Best Season to Visit
Kagamiyama Castle ruins can be visited throughout the year, but each season has its own charm.
Spring (Late March to Early April): Known as a cherry blossom viewing spot, you can enjoy the cherry blossoms blooming on the mountaintop and along the hiking trails. It’s also a time when it’s bustling with cherry blossom viewers.
Summer (June to August): The greenery is lush, and the shade of the trees is pleasant. However, temperatures are high and there are many insects, so sufficient heat protection and insect repellent are necessary.
Autumn (October to November): The autumn leaves are beautiful, and the weather is suitable for hiking. It’s arguably the most comfortable season to enjoy exploring the castle ruins.
Winter (December to February): The air is clear, the views are excellent, and you can see far into the distance. However, temperatures are low, and there is a possibility of snow and ice, so cold weather gear and checking your footing are important.
Photography Tips
Kagamiyama Castle Ruins are also attractive as a photography spot.
- Panoramic View from the Main Enclosure: The panoramic view of the Saijo Basin is a must-see. The morning and evening hours, when the light is beautiful, are especially recommended.
- The Impressive Moat: Photographing the deeply excavated moat from various angles conveys its immense scale.
- The Texture of the Stone Walls: Close-up shots of the rough-hewn stone walls capture the simplicity and strength of the Sengoku period’s construction techniques.
- The Expansion of the Enclosures: Combining the flat areas of the wide enclosures with the surrounding earthworks in your photographs makes the castle’s structure easier to understand.
Visit After Learning About History
Learning about the history of Kagamiyama Castle, especially the conflict between the Ouchi and Amago clans and the exploits of Mori Motonari, beforehand will allow you to enjoy your visit to the castle ruins more deeply.
While there are detailed explanations on the on-site information boards, we recommend doing some research beforehand using related books or websites. Understanding how mountain castles were used and the battles fought there during the Sengoku period allows us to grasp the meaning embedded in each of the remaining structures.
Summary
Kagami-yama Castle (Higashihiroshima City, Hiroshima Prefecture) is a valuable cultural asset designated as a National Historic Site, representing a large-scale mountain castle from the Sengoku period. It played a crucial role as a base for the Ouchi clan’s rule over Aki Province and was the stage for conflicts with the Amago clan.
Built on a mountaintop 335 meters above sea level, the castle ruins, including baileys, moats, vertical trenches, cliffs, stone walls, and well remains, are well-preserved, allowing visitors to experience the structure of a Sengoku period mountain castle. The view from the main enclosure is magnificent, offering a breathtaking panorama stretching from the Saijo Basin to the Seto Inland Sea.
Currently, it is maintained as Kagami-yama Park, with multiple access routes, making it relatively safe even for beginners. It’s easily accessible from JR Saijo Station, and there are other tourist attractions nearby, such as Saijo Sake Brewery Street, making it an area you can enjoy for a full day.
As a mountain castle ruin that conveys the memories of the Sengoku period, it is a recommended spot not only for history buffs but also for those who enjoy hiking and nature walks. Why not visit the Kagamiyama Castle ruins and reflect on the Sengoku period 500 years ago?
