Murals inside Arjai Grottoes in Otog Banner of Ordos, north China's Inner Mongolia Autonomous Region, Sept. 4, 2018. (Xinhua/Jia Lijun)

The grottoes, home to nearly 1,000 frescoes related to Tibetan Buddhism, are located on a hill in the grasslands of Otog Banner, Ordos City, along with other ancient structures including temples and palaces.

HOHHOT, Oct. 23, 2019 (Xinhua) -- Cultural heritage workers launched a program to restore the frescoes of the 1,600-year-old Arjai Grottoes in August 2018. By now, the reinforcement to the rock mass of the grottoes has almost been done with the whole program expected to finish in 2021.

The structures were put under state-level protection in 2003.

The Arjai Grottoes under reinforcement in Otog Banner of Ordos, Oct. 17, 2019. (Xinhua/Jia Lijun)

The Arjai Grottoes in Otog Banner of Ordos, Oct. 17, 2019. (Xinhua/Jia Lijun)

The Arjai Grottoes in Otog Banner of Ordos, Sept. 4, 2018. (Xinhua/Jia Lijun)■