The building, buried in the 51-meter-high, pyramid-like earth above the tomb's main body underground, has four surrounding stair-like walls and each wall with nine steps of platforms, said Duan Qingbo, a researcher with Shaanxi Institute of Archaeology.

The whole building were buried under the earth, which made it difficult for researchers to get a complete picture of it, according to Duan.

Duan said he believed the building may have been built for the soul of the emperor to go out.

Duan said they began to carry out research on the mausoleum's internal structure in 2002 with remote sensing technology, for it has not been allowed to be excavated.

The Qinshihuang's mausoleum is located near Xi'an, capital of northwest China's Shaanxi Province.

In the 1970s, about 1,500 terracotta warriors and horses were unearthed from surrounding pits of the mausoleum. Warriors and horses were believed to be buried with Qin in order to safeguard him after his death.

Qinshihuang, who unified China in 221 BC, became the first emperor of a unified China.