Photo taken on April 11, 2018 shows the outside view of Kaliningrad Stadium which will host the 2018 World Cup matches in Kalininggrad, Russia. (Xinhua/Wu Zhuang)

Photo taken on April 11, 2018 shows the inside view of Kaliningrad Stadium which will host the 2018 World Cup matches in Kalininggrad, Russia. (Xinhua/Wu Zhuang)

Photo taken on April 11, 2018 shows the inside view of Kaliningrad Stadium which will host the 2018 World Cup matches in Kalininggrad, Russia. (Xinhua/Wu Zhuang)

Photo taken on April 11, 2018 shows the outside view of Kaliningrad Stadium which will host the 2018 World Cup matches in Kalininggrad, Russia. (Xinhua/Wu Zhuang)

Photo taken on April 11, 2018 shows the inside view of Kaliningrad Stadium which will host the 2018 World Cup matches in Kalininggrad, Russia. (Xinhua/Wu Zhuang)

Photo taken on April 15, 2018 shows the inside view of Ekaterinburg Arena which will host the 2018 World Cup matches in Ekaterinburg, Russia. (Xinhua/Wu Zhuang)

Photo taken on April 15, 2018 shows the outside view of Ekaterinburg Arena which will host the 2018 World Cup matches in Ekaterinburg, Russia. (Xinhua/Wu Zhuang)

Photo taken on April 14, 2018 shows the inside view of Ekaterinburg Arena which will host the 2018 World Cup matches in Ekaterinburg, Russia. (Xinhua/Wu Zhuang)

Photo taken on April 15, 2018 shows the temperoray tribune of Ekaterinburg Arena which will host the 2018 World Cup matches in Ekaterinburg, Russia. (Xinhua/Wu Zhuang)

Photo taken on April 14, 2018 shows the inside view of Ekaterinburg Arena which will host the 2018 World Cup matches in Ekaterinburg, Russia. (Xinhua/Wu Zhuang)