More than 1,000 volunteers and tourists trekked along the Sword Gate Pass section of the historic Shu Path in Jian'ge county, Sichuan province, on Saturday.

"It happened to be China's first Cultural and Natural Heritage Day and people took to the path with the intention of arousing public attention to its protection and application for the UNESCO World Natural and Cultural Heritage status," said Gao Yihang, one of the volunteers.

One day earlier, the Sichuan World Heritage Application Office of the Sichuan Provincial Department of Housing and Urban-Rural Development announced in Guangyuan, a city which administers Jian'ge, the text for the formal application had been completed.

In 2015, Sichuan started preparing for the path's application to be included into the UNESCO World Natural and Cultural Heritage List. In March, the application was sent to the Ministry of Housing and Urban-Rural Development for review.

Shu was the ancient name for Sichuan. Shu Path is one of the world's oldest land transport systems, with the longest history, the most complicated landform, the most dangerous road and the most abundant historical ruins, according to Zhang Hu, chief the Sichuan World Heritage Application Office of the provincial housing and development agency.

Construction of the Shu Path linking Sichuan and neighboring Shaanxi province started around 316 BC. It was built on mountains so precipitous that Li Bai (701-762), one of China's most eminent poets, wrote: "Traveling on the Shu Path is as difficult as ascending to heaven."

The Sword Gate Pass is a towering V-shaped mountain pass giving rise to the household Chinese idiom that one man at the pass keeps 10,000 men at bay.

It was the only passageway to North China and the neighboring Wei Kingdom in North China tried to take the pass in order to conquer the Shu Kingdom in the Three Kingdoms period (220-280). But not a single frontal attack was successful.

The most famous section of the Shu Path is about 600 km long. It starts at Chengdu, passes Deyang and Guangyuan in Sichuan before ending in Hanzhong in Shaanxi.

When builders approached the Mingyue Gorge in Guangyuan, they could not continue the project as the cliffs were too steep. They had to chisel three levels of holes in the cliffs and inserted wooden beams into the holes.

The upper beams were covered with planks to form a road for pedestrians and the second and third levels held buttresses.

Whenever she mentions her trip to the plank road in Guangyuan a few years ago, Wu Dan, a woman from Beijing, describes her awesome respect for those who built it.