Aerial photo taken on April 18, 2019 shows the Huangyaguan Great Wall in Jizhou District of Tianjin, north China. May 5 marks the opening of "Tianjin Day" theme event at the Beijing International Horticultural Exhibition in Beijing. The city strengthened ecological and wetland protection under the theme of "eco-friendly Tianjin, green development." (Xinhua/Wang Jianhua)