A terrible earthquake struck central China in 1556, killing about 830,000 people.
Most died because they were living in caves made of soft rock, called Loess caves, which collapsed during the quake.
More than 97 counties in the provinces of Shaanxi, Shanxi, Henan, Gansu, Hebei, Shandong, Hubei, Hunan, Jiangsu and Anhui were affected by the 1556 Shaanxi earthquake.
In Huaxian, every single building and home was demolished, killing more than half the people of the city.
Aftershocks continued several times a month for half a year after the initial earthquake.
According to Chinese historical records, the earthquake is often referred to as the Jiajing Great Earthquake.
In more recent times, a 1976 earthquake in Tangshan, China, killed more than 250,000 people.
The earthquake had a magnitude of 8.2.