Aerial photo taken on April 21, 2020 shows a view of the mountainous area in south Jinan, capital of east China's Shandong Province. (Xinhua/Zhu Zheng)

Photo taken on April 21, 2020 shows a view of the mountainous area in south Jinan, capital of east China's Shandong Province. (Xinhua/Zhu Zheng)

Photo taken on April 21, 2020 shows tourists walking on a bridge in the mountainous area in south Jinan, capital of east China's Shandong Province. (Xinhua/Zhu Zheng)

Photo taken on April 21, 2020 shows a view of the mountainous area in south Jinan, capital of east China's Shandong Province. (Xinhua/Zhu Zheng)

Photo taken on April 21, 2020 shows tourists admiring the landscape of the mountainous area in south Jinan, capital of east China's Shandong Province. (Xinhua/Zhu Zheng)

Photo taken on April 21, 2020 shows tourists walking along a path in the mountainous area in south Jinan, capital of east China's Shandong Province. (Xinhua/Zhu Zheng)

Aerial hoto taken on April 21, 2020 shows a view of the mountainous area in south Jinan, capital of east China's Shandong Province. (Xinhua/Zhu Zheng)

Photo taken on April 21, 2020 shows a view of the mountainous area in south Jinan, capital of east China's Shandong Province. (Xinhua/Zhu Zheng)

Photo taken on April 21, 2020 shows a view of the mountainous area in south Jinan, capital of east China's Shandong Province. (Xinhua/Zhu Zheng)