![A view of the entrance to the Nankou Tunnel, part of the Beijing-Zhangjiakou High-speed Railway in Changping District, Beijing, March 28, 2019. Construction of the main structure of the tunnel is now complete. The tunnel is 3,032 meters long and has a designed speed of 250 kilometres per hour. The 174-km-long railway is a major transportation project for the 2022 Winter Olympic Games. (Photo: China News Service/Jia Tianyong)](http://www.ecns.cn/hd/2019/03/29/f40037e80b214155b142d48f620ee292.jpg)
A view of the entrance to the Nankou Tunnel, part of the Beijing-Zhangjiakou High-speed Railway in Changping District, Beijing, March 28, 2019. Construction of the main structure of the tunnel is now complete. The tunnel is 3,032 meters long and has a designed speed of 250 kilometres per hour. The 174-km-long railway is a major transportation project for the 2022 Winter Olympic Games. (Photo: China News Service/Jia Tianyong)
![A worker inside the Nankou Tunnel, part of the Beijing-Zhangjiakou High-speed Railway in Changping District, Beijing, March 28, 2019. Construction of the main structure of the tunnel is now complete. The tunnel is 3,032 meters long and has a designed speed of 250 kilometres per hour. The 174-km-long railway is a major transportation project for the 2022 Winter Olympic Games. (Photo: China News Service/Jia Tianyong)](http://www.ecns.cn/hd/2019/03/29/cf4ff37d2acf4b24a67862916dcec481.jpg)
A worker inside the Nankou Tunnel, part of the Beijing-Zhangjiakou High-speed Railway in Changping District, Beijing, March 28, 2019. Construction of the main structure of the tunnel is now complete. The tunnel is 3,032 meters long and has a designed speed of 250 kilometres per hour. The 174-km-long railway is a major transportation project for the 2022 Winter Olympic Games. (Photo: China News Service/Jia Tianyong)
![A worker inside the Nankou Tunnel, part of the Beijing-Zhangjiakou High-speed Railway in Changping District, Beijing, March 28, 2019. Construction of the main structure of the tunnel is now complete. The tunnel is 3,032 meters long and has a designed speed of 250 kilometres per hour. The 174-km-long railway is a major transportation project for the 2022 Winter Olympic Games. (Photo: China News Service/Jia Tianyong)](http://www.ecns.cn/hd/2019/03/29/7f5b2aea8753415e86705a9f3627b202.jpg)
A worker inside the Nankou Tunnel, part of the Beijing-Zhangjiakou High-speed Railway in Changping District, Beijing, March 28, 2019. Construction of the main structure of the tunnel is now complete. The tunnel is 3,032 meters long and has a designed speed of 250 kilometres per hour. The 174-km-long railway is a major transportation project for the 2022 Winter Olympic Games. (Photo: China News Service/Jia Tianyong)
![A worker inside the Nankou Tunnel, part of the Beijing-Zhangjiakou High-speed Railway in Changping District, Beijing, March 28, 2019. Construction of the main structure of the tunnel is now complete. The tunnel is 3,032 meters long and has a designed speed of 250 kilometres per hour. The 174-km-long railway is a major transportation project for the 2022 Winter Olympic Games. (Photo: China News Service/Jia Tianyong)](http://www.ecns.cn/hd/2019/03/29/1f024c05990f4c4f8724d335d8a05c2a.jpg)
A worker inside the Nankou Tunnel, part of the Beijing-Zhangjiakou High-speed Railway in Changping District, Beijing, March 28, 2019. Construction of the main structure of the tunnel is now complete. The tunnel is 3,032 meters long and has a designed speed of 250 kilometres per hour. The 174-km-long railway is a major transportation project for the 2022 Winter Olympic Games. (Photo: China News Service/Jia Tianyong)