Aerial photo taken on April 10, 2019 shows a view of the Great Wall in Xiangshuihu scenic area in Huairou District of Beijing, capital of China. China's National Cultural Heritage Administration has vowed to strengthen the protection of the Great Wall, which is more than 21,000 km long. The Great Wall, a UNESCO World Heritage Site, consists of many interconnected walls, some dating back 2,000 years. (Xinhua/Hou Dongtao)