Mihara Castle (Hiroshima Prefecture) Complete Guide: History and Highlights of the Coastal Castle Built by Kobayakawa Takakage
Located in Mihara City, Hiroshima Prefecture, Mihara Castle is a unique presence in the history of Japanese castles, built by the renowned Sengoku period general Kobayakawa Takakage. Currently, the castle’s main keep remains directly beneath Mihara Station, a rare sight nationwide. In 2017, it was selected as one of the Continued Top 100 Japanese Castles (No. 172). This article provides a detailed explanation of Mihara Castle, from its history to existing remains and access methods.
Overview of Mihara Castle
Mihara Castle (Mihara-jō) was a Japanese castle located in Mihara, Mitsugi District, Bingo Province (present-day Mihara City, Hiroshima Prefecture), and is designated as a national historic site. It was also known as “Ukishiro” (Floating Castle) and “Gyokko-jō” (Jewel Pot Castle), so named because it appeared to float on the sea at high tide.
Basic Information on Mihara Castle
- Location: 1-chome, Tate-machi, Mihara City, Hiroshima Prefecture
- Year of Construction: Around 1567 (Eiroku 10)
- Builder: Kobayakawa Takakage
- Castle Structure: Coastal castle, terraced flatland castle
- Designated Cultural Property: National Historic Site (part of the Kobayakawa Clan Castle Ruins)
- Continued Top 100 Japanese Castles: No. 172
- Main Lords: Kobayakawa clan, Fukushima clan, Asano clan
Mihara Castle, a coastal castle facing the Seto Inland Sea, also functioned as a base for the Kobayakawa navy. A notable feature is the presence of a ship-entry tower within the castle grounds, allowing for the direct storage of warships.
History of Mihara Castle
Background of Construction and Kobayakawa Takakage
Construction of Mihara Castle began around 1567 (Eiroku 10) by Kobayakawa Takakage, the third son of Mori Motonari. Kobayakawa Takakage is known as one of the “Two Rivers” of the Mori clan and, along with Kikkawa Motoharu, was a warrior who greatly contributed to the expansion of the Mori clan’s power.
Initially, Takakage resided at Takayama Castle (Shin-Takayama Castle), but in order to gain control of the Seto Inland Sea and establish a naval base, he decided to build a new castle by connecting Oshima and Kojima islands in Mihara Bay with stone walls and reclaiming land. This location choice is thought to have been strategically intended to control a key point for maritime traffic.
At the time of its construction, Mihara Castle was a large fortress, stretching approximately 900m from the Yuhara River in the east to the vicinity of Garyu Bridge in the west, and approximately 700m from north to south. The castle complex consisted of the main keep (Honmaru), the second and third baileys (Ninmaru and Sannomaru), and was surrounded by the sea and a moat, creating a strong defensive structure.
Visits by Toyotomi Hideyoshi and Tokugawa Ieyasu
Mihara Castle functioned as an important military base from the Sengoku period to the early Edo period. Records indicate that in 1587, Toyotomi Hideyoshi stopped at Mihara Castle during his Kyushu campaign and met with Kobayakawa Takakage. Tokugawa Ieyasu also visited Mihara Castle around the time of the Battle of Sekigahara, suggesting its importance as a strategic point for controlling western Japan at the time.
Mihara Castle in the Edo Period
After the Battle of Sekigahara in 1600, Kobayakawa Hideaki (Takakage’s adopted son) moved to Okayama Castle, and the family of Fukushima Masanori took up residence in Mihara Castle. When the Fukushima clan was dispossessed of their domain in 1619, Mihara Castle came under the control of Asano Nagaakira, who became the lord of Hiroshima Castle. Asano family members and senior retainers were appointed as castle governors.
Throughout the Edo period, Mihara Castle functioned as a branch castle of the Hiroshima domain, playing a role in monitoring maritime traffic in the Seto Inland Sea. However, with the prolonged period of peace, its military importance as a fortress gradually declined.
Changes after the Meiji Restoration
After the Meiji Restoration, Mihara Castle was abandoned in 1871 with the abolition of the feudal domains and establishment of prefectures. In 1874, many of the castle’s buildings were demolished, and parts of the stone walls were removed.
The most significant change occurred in 1894 when the Sanyo Railway (now the JR Sanyo Main Line) was constructed, passing through the Mihara Castle ruins. During this construction, part of the main keep was removed, and many historical remains were lost. In 1975, the construction of the elevated railway tracks at Mihara Station further affected the remains, but the castle tower base was preserved within the station grounds.
Currently, the Mihara Castle ruins are designated as a national historic site and are protected as part of the “Kobayakawa Clan Castle Ruins Historic Site.” On April 6, 2017, it was selected as one of the Continued Top 100 Japanese Castles, and its historical value has been re-evaluated.
Remains and Highlights of Mihara Castle
Castle Tower Base (Tenshudai)
The most impressive remains of Mihara Castle are the castle tower base, located adjacent to the north exit of JR Mihara Station. It measures approximately 14.5m in height, 22m east-west, and 32m north-south, and its stone walls, a mixture of rough-hewn and fitted stonework, convey its original appearance.
The castle tower base is located under the elevated tracks of Mihara Station, a rare situation nationwide, and can be seen up close from the station platform. The steeply sloping stone walls are impressively constructed, demonstrating the high level of castle-building skills of Kobayakawa Takakage.
While there are no clear records of whether a keep was built on top of the keep platform, it has been suggested that a structure equivalent to a keep may have existed there. Currently, only the stone walls remain, and the upper area has been developed into a plaza, which can be visited free of charge.
Remains of the Ship-Inside Turret
The remains of the Ship-Inside Turret best illustrate Mihara Castle’s characteristics as a coastal castle. This turret was located on the south side of the castle, facing the sea, and was designed to allow warships to be directly brought into the castle at high tide.
Parts of the stone walls of the Ship-Inside Turret still remain, allowing us to imagine the sea level and the way ships entered and left the castle at that time. It is a valuable historical site that concretely demonstrates the function of the castle as a base for the Kobayakawa navy.
Remains of the Main Gate of the Enclosure
The remains of the main gate, which served as the entrance to the main enclosure, also exist. The stone walls and the foundation stones of the gate remain, allowing us to estimate the size of the castle gate at that time. The main gate of the inner citadel was a crucial defensive point, and it is believed that strict security measures were in place.
Stone Walls
Stone walls remain in various locations at the Mihara Castle ruins. Stone walls from different construction periods are mixed together, allowing observation of various construction methods such as rough-hewn stonework, fitted stonework, and cut stonework. These stone walls reveal the history of Mihara Castle’s long-term renovation and maintenance.
Moat Remains
Although now filled in and used for roads and residential areas, a vast moat surrounded the castle. The layout and scale of the moat have been revealed through old maps and archaeological excavations, and research is underway to reconstruct the castle’s layout at the time.
Layout and Structure of Mihara Castle
Mihara Castle had a terraced layout with the main citadel at its center, surrounded by the second and third citadels. The south side, facing the sea, had a boat landing tower and a sluice gate, directly connecting to maritime traffic.
Honmaru (Main Enclosure)
The Honmaru was located in the center of the castle and housed the keep and palace. It was surrounded by high stone walls and a moat, and heavily fortified by castle gates. The area around the current Mihara Station North Exit corresponds to the center of the Honmaru.
Ninomaru and Sannomaru (Second and Third Enclosures)
The Ninomaru and Sannomaru surrounded the Honmaru, each containing samurai residences and barracks. An outer moat encircled the Sannomaru, forming the castle town.
Characteristics as a Coastal Castle
The most distinctive feature of Mihara Castle was that it appeared to float on the sea at high tide. This defensive system, utilizing the ebb and flow of the Seto Inland Sea tides, was essential for its function as a base for the Kobayakawa navy.
The south side of the castle faced directly onto the sea, allowing warships to be stored within the castle via a ship-entry tower. This structure provided strong defense against both land and sea attacks.
Information on the Continued Top 100 Japanese Castles Stamp
Mihara Castle was selected as the 172nd castle in the Continued Top 100 Japanese Castles on April 6, 2017. Two castles from Hiroshima Prefecture were selected: Mihara Castle and Niitakayama Castle. Both castles are designated as National Historic Sites as the Kobayakawa Clan Castle Ruins.
Stamp Locations
The stamps for the Continued Top 100 Japanese Castles are located at the following locations:
- Mihara City Tourism Association (inside Mihara Station)
- Mihara City Board of Education Cultural Affairs Division (Ukishiro Lobby)
The stamps are free to obtain and are available anytime during business hours. Please bring your stamp book and get a stamp as a memento of your castle visit.
How to Visit and Access to Mihara Castle
Access Methods
Access by Train
- Immediately accessible from Mihara Station on the JR Sanyo Main Line and Sanyo Shinkansen
- Convenient access from distant locations as the Kodama Shinkansen stops at this station
- The castle keep can be seen immediately upon exiting the north exit of the station
Access by Car
- Approximately 15 minutes from the Mihara-Kui Interchange on the Sanyo Expressway
- Paid parking is available near Mihara Station
Visiting Hours and Fees
- Visiting Hours: Open 24 hours (outdoor remains such as the castle keep)
- Admission Fee: Free
- Estimated Time Required: Approximately 30 minutes to 1 hour
Major remains such as the castle keep and the boat landing tower are located outdoors and can be freely viewed at any time. However, caution is required regarding safety when visiting at night.
Points to Note During Your Visit
- View the Tenshudai (castle tower base) from Mihara Station North Exit: First, take a look at the entire Tenshudai from the north exit of the station. Pay attention to the steep slope of the stone walls and the magnificent construction.
- Climb to the Top of the Tenshudai: You can climb to the top of the Tenshudai via the stairs. From the top, you can enjoy a panoramic view of Mihara city and experience the perspective of the castle lord at the time.
- Visit the Boat Entrance Tower Ruins: Go around to the south side of the station and visit the Boat Entrance Tower Ruins. This is an important remains that shows the characteristics of a coastal castle.
- Visit the Main Gate Ruins: Don’t miss the Main Gate Ruins, where the stone walls and gate foundation stones remain.
- Utilize Information Boards and Pamphlets: Information boards are installed on site, and the Mihara City Tourism Association distributes pamphlets. Utilizing these will allow you to understand Mihara Castle more deeply.
Nearby Tourist Attractions
When visiting Mihara Castle, we recommend also visiting the nearby tourist attractions:
- Mihara City Historical and Folk Museum: Exhibits materials related to Mihara Castle and the Kobayakawa clan.
- Shintakayama Castle Ruins: The former residence of Kobayakawa Takakage, and like Mihara Castle, selected as one of the Continued Top 100 Japanese Castles.
- Buttsuji Temple: A Zen temple associated with the Kobayakawa clan, also known as a famous spot for autumn foliage.
Toilets and Rest Facilities
Toilets and rest facilities are available within Mihara Station. There are also many restaurants and cafes around the station, which can be used before or after your visit.
Mihara Castle and the Kobayakawa Navy
Mihara Castle was not merely a castle; it also served as the home port for the Kobayakawa Navy. Kobayakawa Takakage led the Mori Navy, gaining control of the Seto Inland Sea and greatly contributing to the expansion of the Mori clan’s power.
Control of the Seto Inland Sea
During the Sengoku period, the Seto Inland Sea was a region where various naval forces, including the Murakami Suigun (Murakami Naval Force), were active. Kobayakawa Takakage, using Mihara Castle as his base, unified these naval forces and secured the Mori clan’s maritime trade routes.
Mihara Castle’s ship-entry tower was designed to allow warships to be stored directly within the castle, enabling rapid sorties. This function made Mihara Castle a crucial maritime base for the Mori clan in the Seto Inland Sea.
Modern Value of Mihara Castle
Historical Value
Mihara Castle occupies an important position in castle history research as a typical example of a coastal castle from the Sengoku to Edo periods. In particular, as a castle with naval-related facilities such as the ship-entry tower, it is a valuable historical site from a military history perspective.
Protection as a Cultural Property
The Mihara Castle ruins, designated as a National Historic Site, require appropriate preservation and utilization. In Mihara City, efforts are being made to preserve and maintain the historical remains, as well as to provide information to visitors through the installation of information boards and the creation of brochures.
Utilization as a Tourism Resource
Having been selected as one of the Continued Top 100 Japanese Castles, Mihara Castle has attracted the attention of castle enthusiasts. Its exceptional accessibility, being just a 0-minute walk from Mihara Station, is a major attraction not found in other castles. Mihara City is working to promote tourism centered around Mihara Castle, and is promoting town development that leverages its history as a castle town.
Comparison of Mihara Castle and Hiroshima Castle
Besides Mihara Castle, Hiroshima Prefecture also has another famous castle, Hiroshima Castle. Both castles are associated with the Mori clan, but their characteristics differ significantly.
Hiroshima Castle is a flatland castle built by Mori Terumoto and functioned as a political and administrative center. On the other hand, Mihara Castle is designed as a coastal castle, emphasizing its military role. Its nickname, “Floating Castle,” which appears to float on the sea at high tide, also well reflects Mihara Castle’s unique characteristics.
Summary
Mihara Castle was a coastal castle built by Kobayakawa Takakage around 1567, serving as an important base for controlling the Seto Inland Sea. Currently, remnants such as the castle tower base and the remains of the boat entrance turret remain, and it is designated as a National Historic Site and one of the Continued Top 100 Japanese Castles.
Its exceptional accessibility, being just a 0-minute walk from JR Mihara Station, is particularly noteworthy among castles nationwide. The unusual situation of the castle tower base remaining beneath the elevated train tracks symbolizes the coexistence of modernization and historical heritage.
When visiting Mihara Castle, take your time to admire the magnificent stone walls of the castle tower base, the remains of the boat entrance turret, and the remains of the main gate, and imagine the appearance of the coastal castle built by Kobayakawa Takakage. It is a castle with a unique charm, befitting its nickname, “Floating Castle,” which is said to have appeared to float on the sea at high tide.
The Mihara City Tourism Association distributes pamphlets and guide maps about Mihara Castle, where you can obtain more detailed information. Don’t forget to get your stamp for the Continued Top 100 Japanese Castles, and fully enjoy the history and charm of Mihara Castle.
