4. Emperor Qinshihuang's Mausoleum, Shaanxi province

With an area of 56 square kilometers, Emperor Qinshihuang's Mausoleum is the world's largest underground mausoleum.

This mausoleum of the first emperor of Qin Dynasty (221-206 BC) is located at the northern foot of Lishan Mountain, 35 kilometers northeast of Xi'an, capital of Northwest China's Shaanxi province.

An army of more than 7,000 life-sized terracotta warriors and horses was discovered at the site of the tomb in 1974. In 1987, it's inscribed in the World Heritage List of UNESCO.