Tourists visit the Blue Moon Valley in Lijiang, southwest China's Yunnan Province, April 21, 2019. (Xinhua/Hu Chao)

Aerial photo taken on April 21, 2019 shows the scenery of Blue Moon Valley in Lijiang, southwest China's Yunnan Province. (Xinhua/Hu Chao)

Aerial photo taken on April 21, 2019 shows the scenery of Blue Moon Valley in Lijiang, southwest China's Yunnan Province. (Xinhua/Hu Chao)

Aerial photo taken on April 21, 2019 shows the scenery of Blue Moon Valley in Lijiang, southwest China's Yunnan Province. (Xinhua/Hu Chao)

Aerial photo taken on April 21, 2019 shows the scenery of Blue Moon Valley in Lijiang, southwest China's Yunnan Province. (Xinhua/Hu Chao)

Aerial photo taken on April 21, 2019 shows the scenery of Blue Moon Valley in Lijiang, southwest China's Yunnan Province. (Xinhua/Hu Chao)

Aerial photo taken on April 21, 2019 shows the scenery of Blue Moon Valley in Lijiang, southwest China's Yunnan Province. (Xinhua/Zi Qiang)