This mobile photo taken on Sept. 8, 2020 shows a city view in Vienna, Austria. (Xinhua/Guo Chen)

This mobile photo taken on Sept. 8, 2020 shows a city view in Vienna, Austria. (Xinhua/Guo Chen)

This mobile photo taken on Sept. 8, 2020 shows a city view in Vienna, Austria. (Xinhua/Guo Chen)

This mobile photo taken on Sept. 8, 2020 shows a city view in Vienna, Austria. (Xinhua/Guo Chen)

This mobile photo taken on Sept. 8, 2020 shows a city view in Vienna, Austria. (Xinhua/Guo Chen)