Aerial photo taken on Sept. 23, 2020 shows tourists taking a boat to view the Caka Salt Lake in Wulan County, northwest China's Qinghai Province. The naturally crystallized saline lake, with an altitude of 3,100 meters, is known as the "mirror of the sky." Photo:Xinhua

Aerial photo taken on Sept. 23, 2020 shows a view of the Caka Salt Lake in Wulan County, northwest China's Qinghai Province. The naturally crystallized saline lake, with an altitude of 3,100 meters, is known as the "mirror of the sky." Photo:Xinhua

Aerial photo taken on Sept. 23, 2020 shows a view of the Caka Salt Lake in Wulan County, northwest China's Qinghai Province. The naturally crystallized saline lake, with an altitude of 3,100 meters, is known as the "mirror of the sky." Photo:Xinhua

Aerial photo taken on Sept. 23, 2020 shows tourists visiting the Caka Salt Lake in Wulan County, northwest China's Qinghai Province. The naturally crystallized saline lake, with an altitude of 3,100 meters, is known as the "mirror of the sky." Photo:Xinhua