Nagaoka Palace Ruins

Nagaoka-kyū Site: Ruins of Emperor Kanmu's Ten-Year Capital

For exactly ten years, between the eleventh month of Enryaku 3 (784) and the tenth month of Enryaku 13 (794), Japan's imperial court governed the country from a palace built on the low Mukōoka Hills, about fifteen kilometers southwest of present-day Kyoto. The capital was called Nagaoka-kyō; its government quarter, where the emperor lived and held audience, was the Nagaoka Palace, or Nagaoka-kyū. Then the court moved again, this time to Heian-kyō, and the older palace was dismantled, its timbers and tiles carried off for reuse. For more than a thousand years afterward, the precise location of the palace itself was a matter of educated guesswork.

Today the throne hall foundation has been excavated, marked with stone, and turned into a neighborhood park in Mukō City, Kyoto Prefecture. The grass-covered rectangle in the middle of Daigokuden Park is the actual stylobate (40.3 meters east-to-west, 21.6 meters north-to-south) on which Emperor Kanmu received his officials. A second park immediately to the north preserves the smaller foundation of the Shōan-den, the rear chamber where the sovereign withdrew between ceremonies. Both have been National Historic Sites since 1964, with successive additions of land continuing as recently as 2016.

Why Kanmu Built a New Capital Here, and Why He Left

The decision to abandon Heijō-kyō (Nara) in 784 was political, religious, and practical at once. Emperor Kanmu had come to the throne in 781 from a branch of the imperial line—the Tenchi line—that had been out of power for nearly a century. He wanted distance from the powerful Buddhist establishments of Nara, whose abbots had grown into political actors during the previous reigns, and he wanted to signal that his accession opened a new chapter. There was also a basic logistical problem with the Nara basin: it had no large river, and bulk goods had to be hauled overland.

Nagaoka sat at the meeting point of the Katsura, Uji, and Kizu rivers, where they join to form the Yodo. That made it a natural hub for grain shipments and timber. Construction began in 784 under Fujiwara no Tanetsugu, Kanmu's most trusted advisor. The plan borrowed the rectangular grid of Tang-dynasty Chang'an and was, on paper, larger in total area than Heijō-kyō.

What followed reads almost like a curse story, and to people at the time, that is what it was. In the ninth month of 785, Tanetsugu was shot dead by arrows during a night inspection of the construction site. The investigation implicated Crown Prince Sawara, the emperor's younger brother. Sawara was stripped of his rank and ordered into exile; he refused food in protest of his innocence and died on the journey to Awaji. Within a few years, plague and famine swept through Nagaoka, two of Kanmu's consorts died, and the new crown prince fell gravely ill. Court diviners pointed to Sawara's vengeful spirit. By 793 Kanmu had ordered scouts to find a new site, and in the tenth month of 794 he transferred the capital to what is now Kyoto.

How the Site Was Rediscovered

Nagaoka-kyō was deliberately erased. Heijō-kyō and Heian-kyō are extensively studied, partly because they survived in some form, but Nagaoka was reduced to farmland within a generation. By the nineteenth century historians sometimes placed it in entirely the wrong district.

The rediscovery owed almost everything to one local schoolteacher. Nakayama Shūichi, a Mukō-born educator and amateur archaeologist, began surveying the area in 1954 on his own initiative, persuading farmers to let him dig test pits between their fields. In 1959 a housing development on the north edge of the suspected palace ground uncovered the remains of a gate; in 1961 Kyoto University took over with a formal academic survey and confirmed the footing stones of the Shōan-den and the stone paving that ran around the Daigokuden stylobate. The Agency for Cultural Affairs designated the two halls as a National Historic Site three years later, in April 1964.

Excavations have continued ever since, and each new discovery has triggered another addition to the protected area: the inner-palace corridor (1973), a long section of earthen wall found during a road-widening project in 1979, the post pits of ceremonial banners discovered in front of the throne hall in 1997, and several other elements through 2016. The total protected ground now exceeds 15,700 square meters across multiple small parcels scattered through Mukō City.

What You Can See

Visitors should understand from the outset that nothing has been rebuilt in three dimensions. There is no replica throne hall and no immersive set-piece. What the parks offer instead is direct contact with the actual ground on which the events of the late eighth century took place.

Daigokuden Park presents the stylobate of the throne hall as a slightly raised, grass-covered rectangle, with the positions of the foundation stones indicated. Three staircases descended from the south face (a central one and one to each side); a fourth set ran down the north face toward the Shōan-den. A large stone stele inscribed "Site of the Daigokuden of the Nagaoka Palace" stands at the south edge. The smaller park across the street preserves the Shōan-den foundation, where the building footprint of seven bays by two has been mapped onto the surface.

A short walk away is Chōdō-in Park, marking the western fourth hall of the council chambers, where senior officials assembled for state business. About thirty meters south of the throne hall foundation, archaeologists in 1997 found a row of large post holes belonging to the hōdō—ceremonial banner masts hoisted on New Year's morning to display the four directional beasts (azure dragon, white tiger, vermilion bird, black tortoise) along with images of bird, sun, and moon. Seven were planned in a single line; three on the east side and two on the west have been confirmed. Their precise rigging is still debated.

To make sense of all this, the Mukō City Cultural Museum, a ten-minute walk from the palace ground, is essential. It was built in 1984 to mark the twelfth centenary of the capital's founding, and its permanent gallery displays mokkan (inked wooden tablets used as government memos), roof tiles, scale models of the Daigokuden and council chamber complex, and a touch-panel "virtual Nagaoka-kyō" 3D map that reconstructs the city as a whole. Admission is free.

Visiting and Nearby

The Daigokuden and Shōan-den parks are open ground with no gate, no admission fee, and no closing time. Hankyū Nishi-Mukō Station, on the Hankyū Kyōto Line between Ōsaka and central Kyoto, is a five-minute walk south of the throne hall site. The Cultural Museum is closer to Hankyū Higashi-Mukō Station, the next stop toward Kyoto, and is open from 10:00 to 18:00 (last entry 17:30), closed Mondays and certain other days.

Mukō City marks the founding date of the capital each year on November 11 with the Daigokuden Festival, and the broader Mukō City Festival on a mid-November weekend includes a procession in reconstructed Nara-period court costume that winds through the streets. Nearby attractions include Mukō Shrine, whose precincts contain a Muromachi-period main hall designated a National Important Cultural Property, and Yanagidani Kannon (Yōkoku-ji), a quiet hillside temple known for hydrangeas in early summer. For travelers continuing south, Nagaokakyō City contains additional palace remains and the Nakayama Shūichi Memorial Hall, devoted to the schoolteacher whose patient fieldwork made all of the above possible.