TAIYUAN, March 20 (Xinhua) -- Archaeologists said they have found the foundations of seven houses in pentagonal structure dating back around 5,500 years in north China's Shanxi Province, providing new clues to the origin of cave dwellings.

The house foundations, facing north and a river, were discovered at the Neolithic ruins in Degang, a village in the city of Lvliang. The largest foundation covered an area of over 130 square meters, and the other ones were about 20 square meters, according to the Shanxi provincial archaeological research institute.

Zhang Guanghui, a researcher with the institute, said the pentagonal house foundations were popular about 5,500 years ago, and have been discovered mainly in Henan, Shanxi and Shaanxi provinces.

The largest one is relatively well preserved and consists of a gateway, fire pit, living space, walls and other parts. Several pieces of pottery were unearthed in the southeast corner of the living space.

Zhang said that according to their discoveries, the remaining original walls of the foundations were up to now the earliest curved walls found by Chinese archaeologists, which was expected to bring the history of cave dwellings from the late stage to the middle stage of Yangshao Culture.

The Yangshao Culture, dating back to 5,000 to 7,000 years ago, originated on the middle reaches of the Yellow River and is considered an important stream of Chinese civilization.