Located about 17km south of Phnom Penh, Choeung Ek was once an orchard and a Chinese graveyard. It was used by the Khmer Rouge regime as an execution ground to put down thousands of people between 1975 and 1979. The site is now better known as the Killing Fields. Mass graves containing thousands of bodies were discovered at Choeung Ek after the fall of the Khmer Rouge regime. Many of the dead were former inmates in the Tuol Sleng prison.

Today, Choeung Ek is a memorial, marked by a Buddhist stupa. The stupa has acrylic glass sides and is filled with more than 5,000 human skulls; many of which are either shattered or had evidently been smashed. It is believed that the Khmer Rouge soldiers kill their victims by smashing them on the head, in order to save on bullets.