CHANGCHUN, June 21 (Xinhua) -- Chinese archaeologists have discovered a group of ancient tombs shaped like pyramids, dating back at least 3,000 years, in Jiaohe City of northeast China's Jilin Province.

    The tombs, covering an area of 500,000 square meters (1,000 meters long and 500 meters wide), were found after water erosion exposed part of a mountain, revealing two of the tombs.

    Six smaller tombs had eroded away leaving no indications of their original scale and appearance, but the biggest tomb, located on the south side of the mountain, could clearly be discerned as a pyramid shape with three layers from bottom to top.

    The pyramid's square bottom is about 50 meters long and 30 meters wide, about the size of a basketball court, with an oval platform on the top, about 15 meters long and 10 meters wide. The tomb was made of stone and earth dug out from the hill.

    A stone coffin, surrounded by four screen boards and covered by a granite top, was placed on the top platform.

    The coffin appeared to belong to the king of an early tribe based on the dimensions of the site, according to experts with the Jiaohe Archaeological Research Institute.

    The tombs are part of the Xituanshan cultural ruins site, which dates back 3,000 years to China's Bronze Age period. The ruins were excavated in Jilin in 1950.

    A lot of ancient hunting and domestic tools, including a stone knife and axe, as well as bronzeware and earthenware, have been unearthed from the stone coffin and other six smaller graves.

    The discovery will provide valuable clues on study of ancient funeral customs and the tomb structure and culture of ethnic groups in the area. Enditem