URUMQI -- The Kizil Grottoes, a UNESCO World Heritage site in Northwest China's Xinjiang Uygur autonomous region, began free entry for the public since Monday.

The popular tourist destination in Baicheng county, Aksu prefecture, will be open to visitors free of charge till April 30, 2021, according to the research institute of the site.

Online reservations started in April this year, allowing tourists to book a trip one week in advance.

Built in the third century, the Kizil Grottoes are among China's earliest sites of large-scale Buddhist grottoes. With 10,000 square meters of frescoes and colorful sculptures, they reveal the history of Buddhism spreading eastward via the western region.