Photographer Li Zhensheng had a unique view of China’s Cultural Revolution—a chaotic period of purging and punishment that began on May 16, 1966, and lasted in different phases until Communist Party Chairman Mao Zedong’s death 10 years later.

Li was working for a newspaper in Heilongjiang Province at the time, and the job allowed him to take state-approved pictures of Mao’s campaign without fear of harassment. He later hid the negatives under his floorboards in case government officials ever came looking for him.

And they did. In 1968, the government accused him of “counterrevolutionary” activities and raided his apartment.

If officials had found the negatives, they likely would have destroyed them. But the images remained hidden under the floorboards, and Li continued to protect them through the years. Today, his remarkable photos have toured the world and been published in a book.

Here, we present mosaics of Li’s images, which show the incredible scale of the Cultural Revolution.

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View Images People gather at the Heilongjiang Province Exhibition Center Theater in 1973. Political struggles within the Communist Party and local governments were bubbling up by this point. Photograph by Li Zhensheng, Contact Press Images

View Images Peasants from the countryside read a letter from the Communist Party addressed to Chinese peasants in Shangzhi County in 1968. Photograph by Li Zhensheng, Contact Press Images

View Images A group reads quotes from Mao at the Harbin Railway Station in 1967. Millions of people were killed, injured, or imprisoned during the revolution. Photograph by Li Zhensheng, Contact Press Images

View Images People celebrate National Day—the founding of the People’s Republic of China—on October 1, 1966, in Red Guard Square. Photograph by Li Zhensheng, Contact Press Images

View Images Leaders of the Heilongjiang Revolutionary Committee meet with others at a conference at the North Plaza Hotel in Heilongjiang Province in 1973. Photograph by Li Zhensheng, Contact Press Images

View Images Young people and peasants work on an irrigation system at the Xisheng Commune in Baiquan County in 1975. Photograph by Li Zhensheng, Contact Press Images

View Images The closing ceremony for an event is held in Red Guard Square, Harbin, in 1968. Photograph by Li Zhensheng, Contact Press Images

View Images A ceremony opens a Harbin gathering in 1968. Photograph by Li Zhensheng, Contact Press Images