Starting from Golmud City in northwest China's Qinghai Province, the Qinghai-Tibet Highway winds south through the mighty Kunlun Mountains while the rivers of Chumar and Tuotuohe snake through along the way. A green van from the state-owned China Post crosses a vast landscape of ice, snow, mountains and rivers.

Every week, Ge Jun, a courier for China's Post's Golmud branch, carries parcels along the route between Golmud and the township of Dangla in Qinghai. The area has an average altitude of 4,500 meters. The delivery route was launched in 2009.

"One round-trip on the route is about 900 km, and so far I have covered about 450,000 km," said Ge, 43. "The distance between Earth and the moon is 380,000 km, which means I have already landed on the moon in that sense!"

China's booming e-commerce has led to a rising number of parcels, with the country's express delivery sector having handled 50.7 billion parcels last year, an annual increase of 26.6 percent, according to the State Post Bureau. Meanwhile, the sector generated 603.8 billion yuan (90 billion U.S. dollars) of revenue, up 21.8 percent.

For Ge, transporting the parcels on the Qinghai-Tibet Plateau is no easy job. The route boasts one of the most hostile conditions on Earth, with the atmosphere consisting of only 43 percent of the oxygen found in the plains. The annual average temperature is minus 6 degrees Celsius, and the average number of days with strong gales is 168.

But perhaps the most difficult part of Ge's itinerary is a 100-meter-high mountain ladder known as the "Sky Ladder."

"I still remember carrying a 10-kg parcel while climbing up the ladder in minus 15 degrees Celsius; all I could hear was my heavy breathing," Ge recalled. "Eight years ago I climbed up the ladder for the first time. I felt dizzy halfway up, and I had to rest frequently to finish my journey."

"The route is probably the world's longest and highest rural route for deliveries," said Bao Junfeng, with the China Post Golmud branch.

Due to years of work in high altitudes, Ge's lips look purple. Frequent attacks of altitude stress, influenza and inflammation have caused him to lose three of his teeth.

Last year, the company organized a medical examination for the couriers, and Ge was diagnosed with two kidney stones. "My family was nervous about my health and urged me to take an operation, but I was so attached to my job that I just couldn't make time for it," he said.

Ge takes turns with his colleagues to work the "sky route" delivery. Each courier drives one of China Post's signature green vans amid the snow-capped Kunlun Mountains and biting cold.

"Because the route is so long, often the meals we take with us in the morning would become too cold to eat when we were ready to have breakfast," Ge said.

Last year, a river at the altitude of 4,570 meters blocked Ge's way after flooding a road on the route.

"I was stranded there for three days," he said.

For Ge, taking the route is mostly about "driving in the daylight and watching stars at night," he said.

Sometimes, Ge would encounter injured wild animals like Tibetan antelopes on the road. He would immediately contact local wildlife rescuers to help them.

Ge also helped some people on his way. In 2012, Ge found a cyclist from Taiwan who passed out due to a physical breakdown. He helped the man into his van and treated his injuries with the first-aid kit.

"In very remote areas of China, mostly only the China Post provides delivery services," Ge said. "I may be alone on the long road, but I am proud of my job."