The £2.6bn motorway that was one of the world’s most 'difficult to build'

The 149-mile long Yaxi Expressway has been described as one of the “most difficult” roads to build. (Image: 王晓东)

This incredible road has been dubbed the “highway in the clouds” - thanks to the fact it rises around 7.5 metres per kilometre and its imposing infrastructure.

It has become one of China’s best roads, connecting the city of Ya’an to the city of Xichang in the southwestern province of Sichuan. It also passes through the sacred Lugu Lake, famous as the home of the Mosuo people and its last matriarchy society in China.

The M-shaped motorway, a section of the Beijing-Kunming highway, was said to be the "most difficult" road in the world to build - costing a staggering £2.6 billion to produce.

Construction of the project was started by the government in 2007 and was completed just five years later, an incredible feat considering that the motorway is made up of 270 viaducts and 25 tunnels. 

It was hoped the road would improve the impact on the environment, with spiral tunnels used to reduce the effect on mountains.

The Yaxi Expressway passes across 12 earthquake fault zones and stretches through hazardous terrain. (Image: Getty)

The geographical conditions in Sichuan made it hard for construction workers to complete the project, with more than half of the tunnels and viaducts travelling through the mountains. 

It also passes across 12 earthquake fault zones and stretches through hazardous terrain. 

On top of this, construction engineers and workers also had to face issues with gas, water sprouting, faults and rocks bursting. 

The Ganhaizi and Tiezhaizi dual spiral tunnels were one of the world's first of its kind with small radiuses. 

Nibashan tunnel is the deepest tunnel in China, with a depth of 1,650 metres and a length of 9,962 metres on the left line and 10,007 on the right line.

Ganhaizi Bridge is one of the most impressive and difficult to build on the Yaxi Expressway. Sitting at an altitude of 2,500 metres, or 8,200 feet, it has a total length of 1,811 metres and a width of 24.5 metres with a total of 36 spans. The highest steel tube truss structure reaches 117 metres.

It was also hoped the road would play a role in helping millions of Tibetan, Han, Yi and Hui people out of poverty, by supporting sustainable local economic growth in western Sichuan, an area rich in natural resources.

Thousands of tourists and residents visit this road to explore the picturesque route on offer, with mountains lining the impressive road.

The road is open year-round, but it is always recommended to check the weather before embarking on the journey as it is a zone known for quickly changing weather conditions.