Photo taken on Aug. 11, 2020 shows the view of Yulin Grottoes in Guazhou County of Jiuquan, northwest China's Gansu Province. Yulin Grottoes are located in the Yulin River valley. They were among the first group of cultural relics to be given state protection in 1961. (Xinhua/Ma Xiping)

Photo taken on Aug. 11, 2020 shows the view of Yulin Grottoes in Guazhou County of Jiuquan, northwest China's Gansu Province. Yulin Grottoes are located in the Yulin River valley. They were among the first group of cultural relics to be given state protection in 1961. (Xinhua/Ma Xiping)

Photo taken on Aug. 11, 2020 shows the view of Yulin Grottoes in Guazhou County of Jiuquan, northwest China's Gansu Province. Yulin Grottoes are located in the Yulin River valley. They were among the first group of cultural relics to be given state protection in 1961. (Xinhua/Ma Xiping)

Photo taken on Aug. 11, 2020 shows the view of Yulin Grottoes in Guazhou County of Jiuquan, northwest China's Gansu Province. Yulin Grottoes are located in the Yulin River valley. They were among the first group of cultural relics to be given state protection in 1961. (Xinhua/Ma Xiping)

Photo taken on Aug. 11, 2020 shows the view of Yulin Grottoes in Guazhou County of Jiuquan, northwest China's Gansu Province. Yulin Grottoes are located in the Yulin River valley. They were among the first group of cultural relics to be given state protection in 1961. (Xinhua/Ma Xiping)

Photo taken on Aug. 11, 2020 shows the view of Yulin Grottoes in Guazhou County of Jiuquan, northwest China's Gansu Province. Yulin Grottoes are located in the Yulin River valley. They were among the first group of cultural relics to be given state protection in 1961. (Xinhua/Ma Xiping)

Photo taken on Aug. 11, 2020 shows the view of Yulin Grottoes in Guazhou County of Jiuquan, northwest China's Gansu Province. Yulin Grottoes are located in the Yulin River valley. They were among the first group of cultural relics to be given state protection in 1961. (Xinhua/Ma Xiping)

Photo taken on Aug. 11, 2020 shows the view of Yulin Grottoes in Guazhou County of Jiuquan, northwest China's Gansu Province. Yulin Grottoes are located in the Yulin River valley. They were among the first group of cultural relics to be given state protection in 1961. (Xinhua/Ma Xiping)

Photo taken on Aug. 11, 2020 shows the view of Yulin Grottoes in Guazhou County of Jiuquan, northwest China's Gansu Province. Yulin Grottoes are located in the Yulin River valley. They were among the first group of cultural relics to be given state protection in 1961. (Xinhua/Ma Xiping)