Photo taken on April 28, 2021 shows the scenery of Schonbrunn Gardens in Vienna, Austria. (Photo: Xinhua)

Photo taken on April 28, 2021 shows the scenery of Schonbrunn Gardens in Vienna, Austria. (Photo: Xinhua)

Photo taken on April 28, 2021 shows the scenery of Schonbrunn Gardens in Vienna, Austria. (Photo: Xinhua)

Photo taken on April 28, 2021 shows the scenery of Schonbrunn Gardens in Vienna, Austria. (Photo: Xinhua)

Photo taken on April 28, 2021 shows the scenery of Schonbrunn Gardens in Vienna, Austria. (Photo: Xinhua)

Photo taken on April 28, 2021 shows the scenery of Schonbrunn Gardens in Vienna, Austria. (Photo: Xinhua)

Photo taken on April 28, 2021 shows the scenery of Schonbrunn Gardens in Vienna, Austria. (Photo: Xinhua)

Photo taken on April 28, 2021 shows the scenery of Schonbrunn Gardens in Vienna, Austria. (Photo: Xinhua)

Photo taken on April 28, 2021 shows the scenery of Schonbrunn Gardens in Vienna, Austria. (Photo: Xinhua)