The National Library of China is building a new book repository to protect China's ancient literary treasures - and its cultural heritage - for future generations. Wang Kaihao reports.

China is preparing to build a "Noah's Ark" for precious books and documents from ancient times, an official from the National Library of China in Beijing revealed in a recent interview with China Daily.

A National Strategic Repository for Documents will be built in Chengde county, Hebei province, according to Sun Yigang, deputy director of the NLC.

Construction on the repository - which is mostly underground and around 68,000 square meters - will begin this year, and is expected to last until 2021.

"Ancient documents hold a country's history and culture," Sun says. "It's our duty to protect them well."

The NLC is home to around 3 million ancient books and documents - which are defined as those written before 1911, when the monarchy fell - which is the world's single biggest collection of its kind.

"However, the ancient books and documents of the NLC are housed in one place," Sun explains, outlining the motive behind the repository's creation. "If war, a terrorist attack or a natural disaster, such as an earthquake, really happened, irreversible loss would follow.

"For the sake of our culture, having such a facility is as important as repositories guarding a country's oil and food safety."

Sun adds that such document repositories are common in other countries like the United Kingdom, the United States and Norway, according to their survey.

"In these countries, the precious documents from their national libraries will be scattered and housed in different places," he said.

In ancient China, there were similar institutions.