Rediscovering Japan
Rediscovering Japan
Travel (Kagawa Part 4 (Manno/Takamatsu))
by tomizuta
The huge Manno Reservoir. The Sanuki region has a Seto Inland Sea climate with relatively little rainfall. In addition, because the surrounding mountains are not particularly high, the rivers provide only limited irrigation water.
Leaving Kotohira-gu Shrine behind, we next headed to Manno Reservoir, some seven or eight kilometers to the southeast. The Sanuki region has a Seto Inland Sea climate with relatively little rainfall. In addition, because the surrounding mountains are not particularly high, the rivers provide only limited irrigation water. For that reason, reservoirs and irrigation ponds have long played an essential role in agriculture here. This point was underlined in 2025, when Takamatsu recorded the lowest annual precipitation among Japan's prefectural capitals. During this trip through Kagawa Prefecture, I was struck by how many reservoirs and ponds could be seen throughout the region.
Map of the plain south of Kotohira-gu Shrine, where numerous irrigation reservoirs and ponds can be seen scattered across the landscape.
Among them, Manno Reservoir is by far the largest irrigation reservoir in Japan, with a circumference of about 20 kilometers, a surface area of 138 hectares, and a storage capacity of 15.4 million tons of water. It has also been designated a Place of Scenic Beauty by the national government. The reservoir was originally constructed in the early eighth century, but after its embankment collapsed in 818, even officials dispatched by the imperial court were unable to repair it. Kukai was then sent to oversee the project. Making use of the civil engineering knowledge he had acquired in Tang China, he is said to have completed, in only about three months, a vast reservoir with a circumference of eight kilometers and an area of 81 hectares. Subsequent enlargement works during the Edo period and modern times gradually brought it to its present scale. Wanting first to learn more about the history of Manno Reservoir, we visited a facility called Karin Kaikan on the northeastern side of the reservoir, but unfortunately it was closed. As it was Wednesday, it appeared to be the facility’s regular closing day.
We wanted to learn more about Manno Reservoir, but unfortunately Karin Kaikan was closed on the day of our visit (left). However, we found a helpful map of the area in the adjacent car park (right). The red sign in the middle shows Karin Kaikan. It is on an elevated plain slightly north of Manno Reservoir.
With no other choice, we turned back and returned to the shore of Manno Reservoir. There we found a parking area and several explanatory signboards about the reservoir. Unfortunately, the information was provided only in Japanese, but the explanations were quite detailed. What particularly struck me was learning how repeatedly the embankment had collapsed from the Nara period through the Edo period, with reconstruction and improvement works carried out each time. According to the information boards, the final major reconstruction that produced the reservoir in its present form was completed in 1959.
On the shore stood a monument commemorating the designation of Manno Reservoir as a “World Heritage Irrigation Structure” in 2016. This is not a UNESCO World Heritage designation, but a recognition granted by the International Commission on Irrigation and Drainage (ICID) to historically important irrigation facilities that have made outstanding contributions to agriculture and water management over long periods of time. The program began in 2014, and sites have since been designated individually year by year around the world. As of 2025, about 200 irrigation facilities in more than 20 countries had received the designation, including 56 in Japan.
Where there is water, there is often a guardian deity. Kanno Shrine stands beside Manno Reservoir. It appears to be an ancient shrine. According to the explanatory plaque, it is listed among the 2,861 shrines recorded in the Engishiki, a compilation of laws and regulations assembled in the early ninth century.
(left) The Kanno Shrine is listed among the 2,861 shrines recorded in the Engishiki, a compilation of laws and regulations assembled in the early ninth century. The stone torii gate is said to date from 1470. (right) The explanatory plaque. Unfortunately, there is no English translation.
Climbing into the grounds of Kanno Shrine, which stand on a slightly elevated flat area beside the reservoir, we came upon a stone torii gate said to date from 1470. From the shrine precincts, there is a commanding view over Manno Reservoir.
From the shrine precincts, there is a commanding view over Manno Reservoir.
Leaving Manno Reservoir behind, we decided to visit Takamatsu Castle before returning to Takamatsu Airport. Facing the sea to the north and incorporating seawater into its moats, Takamatsu Castle is regarded, together with Nakatsu Castle and Imabari Castle, as one of Japan’s three great “water castles.” All three face the Seto Inland Sea and were designed in part to defend against attacks from the sea. Takamatsu Castle was constructed in 1590 by Ikoma Chikamasa, a cousin of Oda Nobunaga, after Toyotomi Hideyoshi completed his conquest of Shikoku. In 1639, the Ikoma clan was transferred elsewhere and Matsudaira Yorishige—a grandson of Tokugawa Ieyasu and son of the first lord of the Mito Domain—was installed as lord. At the time of the Ikoma transfer, Sanuki Province was divided into eastern and western domains: the west became the Marugame Domain, while the east became the Takamatsu Domain under the Matsudaira family, ruling from Takamatsu Castle. The Matsudaira remained in control until the Meiji Restoration. The castle was decommissioned in 1869, and its main keep was demolished. However, the castle was not entirely dismantled. In 1890 it was transferred to the former ruling Matsudaira family, and in 1954 it was handed over to the city of Takamatsu. Today it is open to the public as Tamamo Park. We parked in the lot on the southeastern side of the castle grounds and began exploring. It had been drizzling since morning, but by then the rain had become considerably heavier.
The guide map of the castle from the official brochure. The route I traveled starting from the car park at the bottom right is marked in red. The Sakura Gomon Gate I explain below stands just across the moat shown in blue at the center of the map, after crossing from the south (the lower side of the map).
Immediately beside the parking area are the Asahi Bridge crossing the moat and the Asahi Gate of Takamatsu Castle. In Japanese castles, the formal main entrance was usually the Otemon (“Great Gate”), but in the case of Takamatsu Castle, the Otemon on the southern side was abolished, and from fairly early in the Edo period the Asahi Gate appears to have served as the castle’s official entrance instead.
From fairly early in the Edo period the Asahi Gate appears to have served as the castle’s official entrance.
Passing through the Asahi Gate of Takamatsu Castle, we entered a masugata—a small enclosure surrounded by stone walls built just beyond a castle gate. This was a defensive device designed to trap invading enemies in a confined space where they could be attacked from three sides. Beyond it stands an impressive turret known as the Ushitora-yagura. Originally located at the northeastern corner of the castle, it was relocated to the southeastern part of the grounds in 1967. Ushitora refers to the northeast direction in the traditional East Asian system of compass points.
Beyond the Asahi Gate of Takamatsu Castle lay a masugata, a typical defensive feature of Japanese castle architecture (left). The impressive turret known as the Ushitora-yagura (right).
We arrived at the imposing Sakura Gomon gate of Takamatsu Castle, once the entrance leading to the residence of the castle lord. The original gate was destroyed in the 1945 air raid on Takamatsu, but was faithfully reconstructed in 2022. Beyond the gate lies an open square, beside which stands a facility known as the Chinretsukan, exhibiting materials related to the history of Takamatsu Castle. Although the displays are in Japanese, some of the information is separately introduced in English on Takamatsu City’s website, which overseas visitors may find useful to consult. I was impressed by the efforts being made by the city of Takamatsu to restore and preserve the castle.
We arrived at the imposing Sakura Gomon gate of Takamatsu Castle, once the entrance leading to the residence of the castle lord.
The next highlight was a building known as Hiunkaku. Originally, this site was occupied by the castle lord’s palace, a structure somewhat larger than the present Hiunkaku. That earlier building was demolished after the Meiji-era abolition of the castle system because of its deteriorated condition. After the castle grounds were transferred to the Matsudaira family, the current Hiunkaku was constructed in 1917 as their villa and was also used to receive distinguished guests. Today, its various rooms are available for rental for a fee, although the building itself is open to the general public only on limited occasions, such as during the New Year holidays. At the time of our visit, seismic reinforcement work was being carried out in stages throughout the structure.
The Hiunkaku building constructed in 1917 is designated as an important cultural property (left). At the time of our visit, seismic reinforcement work on the Daishoin room (the largest banquet room) was being carried out (right).
The rain intensified, and we hurriedly made our way around the remaining sights, including the site of the former main keep of Takamatsu Castle. The castle offers boat tours around the moats in traditional Japanese-style boats, but at the ticket office near the path leading to the main keep site, a notice announced that departures had been suspended because of the weather. This area forms the Ninomaru. One distinctive feature of Takamatsu Castle is that the Honmaru and the main keep stood independently within the moats. Connecting this Ninomaru area to the Honmaru and the keep site is a single narrow bridge known as Saya-bashi, stretching across the moat.
Connecting the Ninomaru area to the Honmaru and the keep site is a single narrow bridge known as Saya-bashi, stretching across the moat.
Note:Japanese castles often consisted of a Honmaru (main enclosure), Ninomaru (second enclosure), and Sannomaru (third enclosure). The Honmaru formed the political and military heart of the castle. The Ninomaru and Sannomaru were defensive layers positioned in front of it in that order. In many castles, the lord’s day-to-day residence was located in the Ninomaru. In the case of Takamatsu Castle, the palace stood in the Ninomaru during the Ikoma period, but was moved to the Sannomaru under the Matsudaira family. That palace later became the original Hiunkaku. In the map above, the route I followed is shown in red. Entering through the Sakura-no-Gomon (upper right on the map), I proceeded into the Sannomaru and then crossed the moat to the Ninomaru in the upper left area of the map. From there, another narrow bridge crosses the moat to the Honmaru and the site of the main keep. The layout deliberately isolated the Honmaru and the keep almost in the center of the moats in order to strengthen their defenses. Incidentally, Honmaru roughly corresponds to what might be called the “main castle” in English. In Japanese, the expression “to attack the Honmaru” originally meant attacking the very heart of a castle, but today it is also used figuratively in business and everyday language to mean getting to the heart of an issue.
We climbed up to the Honmaru and the site of the foundation stones of the former main keep (left). In truth the remains of the keep are more impressive when viewed from a distance.
back to Kagawa Part 1