The relic of Unit 731 is located in Harbin, northeast China’s Heilongjiang Province. Unit 731 was a secret biological and chemical warfare research base established in Harbin in 1935 as center of Japan's biological warfare in China and Southeast Asia during WWII. From 1939 to 1945, at Least 3,000 people were killed there, and more than 300,000 people perished due to biological weapons. The retreating Japanese invaders blew up the base to cover their crimes before they surrendered in 1945. [Photo: people.com.cn]