Archaeologists have found the remains of an ancient imperial palace near the tomb of emperor Qin Shi Huang, home of the famous terracotta army, China's state media reported on Sunday. The palace is the largest complex discovered so far in the emperor's sprawling 22 square-mile (56 square-km) second-century BC mausoleum, which lies on the outskirts of Xi'an, an ancient capital city in central China, an associate researcher at the Shaanxi provincial institute of archaeology told China's official news wire Xinhua.

It is an estimated 690 metres long and 250 metres wide - about a quarter of the size of the Forbidden City in Beijing - and includes 18 courtyard-style houses with one main building at the centre, according to the researcher, Sun Weigang. Sun called the palace a clear predecessor to the Forbidden City, which was occupied by emperors during the later Ming and Qing dynasties. Both were built on north-south axes in keeping with traditional Chinese cosmology.
© Museum Of The Terracotta Army/PALife-sized terracotta warriors guard the tomb of China's first emperor, Qin Shi Huang, where a huge palace complex has been unearthed.

Despite wars soon after Qin Shi Huang's death - and more than 2,000 years of exposure - the foundations are well preserved. Archaeologists have found walls, gates, stone roads, pottery sherds and some brickwork, according to Xinhua. They have been excavating the foundations since 2010. Qin's tomb is guarded by an estimated 6,000 life-sized terracotta warriors, including remarkably well-preserved cavalrymen, chariots and horses, each one unique. They were first discovered in 1974 by workers digging a well. About 2,000 have been excavated; 110 of them were unearthed this summer.

The United Nations educational, scientific and cultural organisation (Unesco) declared the army a world heritage site in 1987.

Qin began designing the palace for his afterlife shortly after he became king of the Qin state, aged 13. The complex took 700,000 workers about 40 years to build and was completed two years after his death. According to writings by the Han dynasty scholar Sima Qian, Qin Shi Huang's tomb is 120 metres high, sealed off by a vermilion stone wall, surrounded by rivers of mercury and protected by booby traps. It has not been excavated for fear of damaging the potentially priceless artefacts inside.

Chinese historians portray Qin as a great unifier, who conquered six states and established an expansive feudal kingdom with a united currency and writing system. He is also known as a ruthless leader who burned books, buried opponents alive and castrated prisoners of war.