Tourists take photos at the Caka Salt Lake scenic spot at Caka Town of Wulan County, northwest China's Qinghai Province, July 18, 2019. Caka Salt Lake, covering an area of 105 square kilometers and with an altitude of 3,100 meters, attracts many tourists in summer. (Xinhua/Zhang Long)

　　Photo shows the scenery of the Caka Salt Lake scenic spot at dusk in Caka Town of Wulan County, northwest China's Qinghai Province, July 18, 2019. Caka Salt Lake, covering an area of 105 square kilometers and with an altitude of 3,100 meters, attracts many tourists in summer. (Xinhua/Zhang Long)

　　Tourists visit the Caka Salt Lake scenic spot at Caka Town of Wulan County, northwest China's Qinghai Province, July 18, 2019. Caka Salt Lake, covering an area of 105 square kilometers and with an altitude of 3,100 meters, attracts many tourists in summer. (Xinhua/Zhang Long)

　　A tourist train runs in the Caka Salt Lake scenic spot at Caka Town of Wulan County, northwest China's Qinghai Province, July 18, 2019. Caka Salt Lake, covering an area of 105 square kilometers and with an altitude of 3,100 meters, attracts many tourists in summer. (Xinhua/Zhang Long)

　　Tourists view a salt sculpture of the Caka Salt Lake scenic spot at Caka Town of Wulan County, northwest China's Qinghai Province, July 18, 2019. Caka Salt Lake, covering an area of 105 square kilometers and with an altitude of 3,100 meters, attracts many tourists in summer. (Xinhua/Zhang Long)

　　Tourists take photos at the Caka Salt Lake scenic spot at Caka Town of Wulan County, northwest China's Qinghai Province, July 18, 2019. Caka Salt Lake, covering an area of 105 square kilometers and with an altitude of 3,100 meters, attracts many tourists in summer. (Xinhua/Zhang Long)

　　A tourist train runs in the Caka Salt Lake scenic spot at Caka Town of Wulan County, northwest China's Qinghai Province, July 18, 2019. Caka Salt Lake, covering an area of 105 square kilometers and with an altitude of 3,100 meters, attracts many tourists in summer. (Xinhua/Zhang Long)

　　Tourists visit the Caka Salt Lake scenic spot at Caka Town of Wulan County, northwest China's Qinghai Province, July 18, 2019. Caka Salt Lake, covering an area of 105 square kilometers and with an altitude of 3,100 meters, attracts many tourists in summer. (Xinhua/Zhang Long)

　　Photo shows the sunset scenery of the Caka Salt Lake scenic spot at Caka Town of Wulan County, northwest China's Qinghai Province, July 18, 2019. Caka Salt Lake, covering an area of 105 square kilometers and with an altitude of 3,100 meters, attracts many tourists in summer. (Xinhua/Zhang Long)