Visitors walk in the natural environmental zone along the Guishui River at the International Horticultural Exhibition 2019 Beijing in Yanqing District of Beijing, capital of China, April 30, 2019. The International Horticultural Exhibition 2019 Beijing, the largest expo of its kind in the world, opened to the public Monday in Yanqing District. Yanqing boasts itself as being home to parts of the Great Wall. It is a summer resort and the agricultural base of Beijing. The upgrading of infrastructure and the acceleration of the horticulture industry because of the expo can further stimulate the development of tourism in Yanqing. (Xinhua/Zhang Chenlin)