Photo taken on June 17, 2019 shows the inner scenery of Tieling Karst Cave in Huangqizhai Town of Kaiyuan, northeast China's Liaoning Province. (Xinhua/Yang Qing)

　　Photo taken on June 17, 2019 shows the inner scenery of Tieling Karst Cave in Huangqizhai Town of Kaiyuan, northeast China's Liaoning Province. (Xinhua/Yang Qing)

　　Photo taken on June 17, 2019 shows the inner scenery of Tieling Karst Cave in Huangqizhai Town of Kaiyuan, northeast China's Liaoning Province. (Xinhua/Yang Qing)

　　Photo taken on June 17, 2019 shows the inner scenery of Tieling Karst Cave in Huangqizhai Town of Kaiyuan, northeast China's Liaoning Province. (Xinhua/Yang Qing)