Archeologists in northwest China's Shaanxi Province said Wednesday they had found a primitive "icebox" dating back at least 2,000 years in the ruins of an emperor's residence.

The "icebox," unearthed in Qianyang County, contained several clay rings 1.1 meters in diameter and 0.33 meters tall, said Tian Yaqi, a researcher with the Shaanxi Provincial Institute of Archeology.

"The loops were put together to form a shaft about 1.6 meters tall," Tian said.

The shaft was unearthed about 3 meters underground within the ruins of an ancient building which experts believed was a temporary imperial residence during the Qin Dynasty (221 - 207 BC).

"The shaft led to a river valley, but it could not have been a well," said Tian.

A well, he explained, would have been much deeper as groundwater could not have been reached only 3 meters underground in arid northwest China.

"Nor would it have been possible to build a well inside the house."

Tian and his colleagues believe the shaft was an ice cellar, known in ancient China as "ling yin," a cool place to store food during the summer.

A poem in the "Book of Songs" -- a collection of poetry from the Western Zhou Dynasty (11th century -771 BC) to the Spring and Autumn Period (770 - 475 BC) - says food kept in the "ling yin" will to stay fresh for three days in the summer.

"If ice cellars were popular more than 2,000 years ago, it certainly sounds reasonable that the emperor and court officials would have one in their residence," said Tian.

Covering an area of about 22,000 square meters, the shaft and the residence were first discovered by villagers building homes in 2006. The area was immediately fenced off by authorities to protect the heritage site.

Research work began in March this year and ended last week.

(Xinhua News Agency May 26, 2010)