Aerial photo taken on July 4, 2019 shows the scenery of Qujiang Lake Heritage Park in Xi'an, capital of northwest China's Shaanxi Province. (Xinhua/Zhang Bowen)

Aerial photo taken on Nov. 13, 2019 shows the scenery of Daming Palace National Heritage Park in Xi'an, capital of northwest China's Shaanxi Province. (Xinhua/Zhang Bowen)

Aerial photo taken on June 29, 2019 shows the scenery of Daming Palace National Heritage Park in Xi'an, capital of northwest China's Shaanxi Province. (Xinhua/Zhang Bowen)

Aerial photo taken on Nov. 13, 2019 shows the scenery of Daming Palace National Heritage Park in Xi'an, capital of northwest China's Shaanxi Province. (Xinhua/Zhang Bowen)

Aerial photo taken on Nov. 13, 2019 shows the scenery of Daming Palace National Heritage Park in Xi'an, capital of northwest China's Shaanxi Province. (Xinhua/Zhang Bowen)

Aerial photo taken on Nov. 13, 2019 shows the scenery of Daming Palace National Heritage Park in Xi'an, capital of northwest China's Shaanxi Province. (Xinhua/Zhang Bowen)

Aerial photo taken on June 29, 2019 shows the scenery of Daming Palace National Heritage Park in Xi'an, capital of northwest China's Shaanxi Province. (Xinhua/Zhang Bowen)

Aerial photo taken on July 4, 2019 shows the scenery of Qujiang Lake Heritage Park in Xi'an, capital of northwest China's Shaanxi Province. (Xinhua/Zhang Bowen)

Aerial photo taken on June 28, 2019 shows the Xi'an Expo Park located within the Chanba Ecological District in Xi'an, northwest China's Shaanxi Province. (Xinhua/Zhang Bowen)

Aerial photo taken on June 28, 2019 shows the Xi'an Expo Park located within the Chanba Ecological District in Xi'an, northwest China's Shaanxi Province. (Xinhua/Zhang Bowen)

Aerial photo taken on June 28, 2019 shows the Xi'an Expo Park located within the Chanba Ecological District in Xi'an, capital of northwest China's Shaanxi Province. (Xinhua/Zhang Bowen)

Aerial photo taken on June 28, 2019 shows the Xi'an Expo Park located within the Chanba Ecological District in Xi'an, northwest China's Shaanxi Province. (Xinhua/Zhang Bowen)

Aerial photo taken on July 13, 2019 shows the scenery of ancient city wall in Xi'an, capital of northwest China's Shaanxi Province. (Xinhua/Zhang Bowen)