On this day in 1556, the deadliest earthquake in history shook Shaanxi, China, killing about 830,000 people. Counting casualties are often imprecise after large-scale disasters, especially before the 20th century, but this disaster is still considered the deadliest of all time.

The earthquake rocked the city with aftershocks from the late evening to the next morning. Later, a scientific investigation revealed that the magnitude was 8.0-8.3, which isn’t even close to the strongest magnitude. However, the quake struck in the middle of a highly populated area with poorly constructed buildings and homes, resulting in a high death toll.

The epicenter, or the center of the earthquake, was in the Wei River Valley near the cities of Huaxian, Weinan, and Huayin. Every single building collapsed in the city of Huayin, killing more than half of the residents in the city. The earthquake caused some 6-feet-deep crevice openings in the earth. There was still death and destruction even 300 miles away from the epicenter and landslides were triggered by the quake, which also made more death occur.

Even if the number of deaths caused by the Shaanxi earthquake had been overestimated slightly, it would still rank as the worst disaster in history by a considerable margin. The 2004 earthquake/tsunami in Indonesia is generally considered the second deadliest disaster in history.