The remains of a massive "imperial palace" have been uncovered at the mausoleum of China's fist emperor, Qinshihuang, archaeologists announced.

Sun Weigang, an associate researcher at the Shaanxi provincial institute of archaeology, said that based on its foundations, the courtyard-style palace was estimated to be 690 meters long and 250 meters wide.

Covering an area of 170,000 cubic meters, the palace was nearly one fourth the size of the Forbidden City in Beijing, the imperial palace of China's last two feudal dynasties of Ming and Qing (1368-1911), Sun said.

It is the largest complex ever found at the cemetery of Qinshihuang, known as China's first emperor as he united the country, he said.

The palace included 18 courtyard houses and a main building that overlooked the houses, according to the researcher.

The palace could shed light on the architectural styles of the Qin Dynasty (221 BC-207 BC) and showed emperor Qinshihuang's wish to continue to live in imperial grandeur even during his afterlife, he said.

The 56-square-km Mausoleum of Qinshihuang is the world's largest underground mausoleum and is famous for its terracotta warriors.