Among the 20 documents in the grave was the first edition of the Communist Party of China Constitution, published after the Party's second National Congress in 1922, and the Chinese translation of The Communist Manifesto, which was published in 1920.

"More than 20 documents in this historical treasure trove are now classified as Grade A national cultural relics," said Wang Zuqiang, deputy director of the Party History and Literature Research Office of the CPC Zhejiang provincial committee.

The documents are now displayed in a small museum in Shanghai, where the first CPC National Congress was convened in July, 1921.

The Zhang Renya Academy, established by the Ningbo government in 2017, was recently designated as one of the province's fourth batch of red tourism education bases by the Zhejiang Provincial Department of Culture and Tourism.

The 4,600-square-meter academy, which displays copies of 34 documents saved by Zhang, has received more than 100,000 visitors.

The academy is set to be upgraded into a Party education base featuring the Party's history and spirit as China races toward July 1, the 100th anniversary of the CPC's founding, according to the Ningbo city bureau of culture, radio, television and tourism.

Cai Jingwen and Ye Zizhen contributed to this story.