A water channel created with stones is found at the Asukakyo ruins garden-and-pond complex in Asuka, Nara Prefecture. (Yuya Tanaka)

ASUKA, Nara Prefecture--Researchers uncovered a water channel created with stones in the ruins here of an elaborate imperial court garden built in the latter half of the seventh century.

The Asukakyo ruins garden-and-pond complex, which contained two artificial ponds, located north and south, is believed to be the site of Japan’s first court garden adjacent to an imperial palace.

The Archaeological Institute of Kashihara announced that the North Pond features masonry ditches stretching over about 11.5 meters as well as remnants of a stone-paved floor.

Archaeologists said it was likely the site of court water rituals dating to the Kofun Period (late third to seventh centuries).

Asukakyo refers to the ancient capital of Japan established in the fledgling years of the nation.

The garden-and-pond complex, which has been designated by the central government as a “historic site” and “place of scenic beauty,” lies northwest of the Asuka palace ruins, where imperial residences stood during the Asuka Period (592-710).

It contained buildings, ponds, a waterway and other structures within an area measuring 280 meters from north to south and 100 meters from east to west.

A stone water fountain and what appears to be the remains of a "floating stage" have been found at the site of the South Pond.

The latest discovery shows the complex comprised two ponds of different designs and purposes. The North Pond was where rituals were held and the South Pond was where imperial members went to relax and appreciate the scenery.

Workers began excavating a northeastern section of the North Pond in May. They uncovered the remains of a floor, paved carefully with stones measuring 40 to 70 centimeters in size, within an area extending roughly 13 meters from north to south and 8.5 meters from east to west.

The central section of the stone-paved floor featured two square-shaped stone “basins” measuring 80 cm to 1.3 meters on each side and 20 cm to 50 cm in depth, along with stone ditches running in an east-west direction. The width of the ditches ranges from 30 cm to 80 cm.

The entire structure was designed so that spring water gathering in one of the basins flowed into the adjacent ditches. The institute said there appeared to be significance in ensuring that clear water was flowing.

“The area was likely a sacred zone, where emperors or others performed rituals using water,” said Masashi Kinoshita, professor emeritus of archaeology at Tokyo Gakugei University. “The site could be seen as a prototype of Japanese culture, where the concept of a garden-and-pond complex, which originated in China, was merged with the traditional Japanese notion of nature worship.”

Kanekatsu Inokuma, professor emeritus of archaeology at Kyoto Tachibana University, said the area was possibly a site of ablutions, "where emperors purified themselves ahead of rituals and divinations.”

It was previously believed the North Pond had a conical shape with a water depth of 2-3 meters. The discovery of the stone-paved floor shows, however, that the northeast corner of the North Pond was above water.

Inokuma cited the possibility of the emperor descending steps to the stone-paved floor to scoop flowing water from a ditch or pour it over himself for self-purification.

Kosaku Okabayashi, head of the Archaeological Institute of Kashihara’s research department who was involved in the study, speculated the facility was used in rituals for subjugating residents of provinces that were considered frontier zones in those days.

“Nihon Shoki” (Chronicles of Japan), which was completed in the eighth century, states that since the days of Empress Saimei, who reigned from 655 to 661, representatives of the Emishi tribe from the Tohoku region and the Hayato tribe from southern Kyushu were wined and dined in a “square of zelkova trees” to the north of the garden-and-pond complex.

Another passage in the record of ancient Japan says a chief of the Emishi tribe gargled with river water and took an oath of subjugation in 581. The complex may have been the site of similar rituals, Okabayashi said.

(This article was written by Yoshito Watari and Yuya Tanaka.)