Heijo Palace was the political and administrative center of Heijo-kyo, the capital of Japan during the Nara period (710–794). This expansive palace complex included the emperor’s residence, known as the Dairi, as well as ceremonial courtyards, government offices, and other facilities essential to the administration of the ancient state. Covering approximately 120 hectares, it was one of the most important centers of power in early Japanese history.
In December 1998, Heijo Palace Ruins became part of the UNESCO World Heritage Site Historic Monuments of Ancient Nara, together with landmarks such as Todai-ji Temple. Its inclusion was particularly significant because it was the first archaeological site in Japan to receive World Heritage recognition.
Heijo Palace stood at the northern end of Heijo-kyo. The palace grounds were enclosed by substantial earthen walls, approximately five meters high, and had 12 gates bearing names associated with aristocratic family names. The magnificent Suzakumon Gate, located on the southern side, served as the principal entrance and symbolized the authority and grandeur of the imperial court.
At the eastern edge of the complex was the East Palace Garden, a refined landscape used for banquets, ceremonies, and other courtly occasions. Its carefully arranged ponds, stones, and garden features provide valuable insight into the development of Japanese garden design and are considered representative of the foundations of the traditional Japanese garden aesthetic.
Heijo Palace underwent several major renovations and alterations throughout the Nara period. Its buildings and layout changed over time, although the details of these transformations remained unclear for centuries, before modern archaeological investigations began to reveal the original arrangement.
In 784, the capital was transferred to Nagaoka-kyo, and Heijo Palace gradually lost its role as the center of government. Emperor Heijo later established a residence known as Heijo Saigu near the site of the original First Imperial Audience Hall. However, after the capital was permanently established at Heian-kyo, present-day Kyoto, the former palace grounds gradually reverted to agricultural land.
In 1852, during the late Edo period, Kitayasu Sadamasa, an official of the Nara magistrate’s office, created a map entitled Heijo Palace and Inner Palace Ruins: Land-Plot Plan. His work was an important early attempt to identify the location and layout of the ancient palace.
During the Meiji period, architectural historian Sekino Tadashi investigated a raised area in the rice fields and identified it as the foundation platform of the Second Imperial Audience Hall. In 1907, he published his findings in a newspaper article entitled A Study of Heijo-kyo and the Imperial Palace Complex. Although his research helped draw attention to the site, some of his interpretations were later shown to be incorrect.
Sekino’s research inspired preservation advocates, including Tanada Kajuro and Mizobe Bunshiro, to campaign for the protection of the ruins. In 1921, funds donated by local residents were used to purchase the central portion of the former palace grounds, which was then donated to the Japanese government.
In 1922, the site was designated a National Historic Site. It was subsequently elevated to the status of a Special Historic Site, reflecting its exceptional importance to Japan’s cultural heritage.
Archaeological investigations continued throughout the twentieth century. In 1960, research by Kudo Yoshiaki, who participated in investigations conducted by the Nara National Research Institute for Cultural Properties, helped correct earlier interpretations and establish a more accurate location for the emperor’s residential quarters.
During the 1960s, further preservation campaigns arose in response to proposals for railway facilities and road construction that threatened the ruins. Supported by public concern and nationwide efforts, these campaigns helped secure the protection of a much larger area of the former palace grounds.
The Lecture Hall at Toshodai-ji Temple, a National Treasure, is traditionally identified as the only surviving building associated with the original Heijo Palace complex. It is believed to have been relocated from a palace building known as the East Choshuden. Although its roof and other features were modified in later periods, the structure remains an exceptionally valuable example of architecture connected with the Nara-period imperial court.
Research conducted in fiscal year 2015 at the site of the Buraku-in, a ceremonial complex within the imperial palace of Heian-kyo, revealed that its central building, the Burakuden, was approximately the same size as the Second Imperial Audience Hall at Heijo Palace. This discovery prompted speculation that the Second Imperial Audience Hall may have been relocated to Kyoto after the capital moved.
Numerous artifacts have been recovered from the Heijo Palace ruins, including thousands of wooden tablets known as mokkan. These narrow wooden strips were used in ancient Japan for administrative records, correspondence, and other written communications.
A collection of 3,184 wooden tablets excavated at the site was designated a National Treasure in 2017. These materials offer invaluable evidence of the political system, economy, bureaucracy, and everyday life of Japan during the Nara period.
Today, the Heijo Palace ruins form a remarkable historical landscape where visitors can explore the remains of Japan’s eighth-century capital. Reconstructed structures, archaeological sites, and open grounds help convey the scale of the imperial complex and the sophistication of the ancient Japanese state. For travelers interested in Japanese history, architecture, archaeology, and the origins of the capital city, Heijo Palace offers an essential perspective on Nara’s role in shaping the nation.