Photo taken on Sept. 4, 2018 shows murals inside Arjai Grottoes in Otog Banner of Ordos, north China's Inner Mongolia Autonomous Region. 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 according to the administration. (Photos: Xinhua)

Photo taken on Oct. 17, 2019 shows the Arjai Grottoes in Otog Banner of Ordos, north China's Inner Mongolia Autonomous Region. 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 according to the administration.

Photo taken on Sept. 4, 2018 shows the Arjai Grottoes in Otog Banner of Ordos, north China's Inner Mongolia Autonomous Region. 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 according to the administration.

Photo taken on Oct. 17, 2019 shows the Arjai Grottoes under reinforcement in Otog Banner of Ordos, north China's Inner Mongolia Autonomous Region. 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 according to the administration.