A tourist picks melons at a greenhouse in Caofeidian District, Tangshan City of north China's Hebei Province, April 20, 2019. A total of 7,915 greenhouses, covering an area of nearly 2,000 hectares, generate the annual output value of about 210 million yuan (about 31 million U.S. dollars) in Caofeidian District. (Xinhua/Yang Shiyao)