Lhasa is the capital city of Southwest China's Xizang Autonomous Region and the final stop along the Qinghai-Xizang Railway. Over the past two decades, its population has nearly doubled to almost one million. More people have come to the city in search of work, travel opportunities or love. Our reporter Wu Bin follows their stories and explores how the railway brings people together. 

This is the Qinghai-Xizang Railway. Some call it the "Sky Road." Others know it as the "road to happiness." For two decades, it has carried people from across the globe to the roof of the world. Some chose to stay, including 51-year-old Wang Zengcai. Wang now works as a driver instructor at Lhasa West Railway Station in southwest China's Xizang Autonomous Region.

Born in neighboring Qinghai Province, he first arrived in Xizang in 1996 as a truck driver. Back then, a round trip by truck between Golmud and Lhasa took 13 days. At the time, he never imagined he would one day settle on the plateau.

In 2006, just two days before the Qinghai-Xizang Railway officially opened, he served as an assistant driver and helped bring the first shunting locomotive from Golmud into Lhasa West Station.

WANG ZENGCAI, Driver Instructor, Lhasa West Railway Station "Of course I was excited. It was the first shunting locomotive at Lhasa West Station. That trip took about 32 hours. It was much faster."

Later, he met a Tibetan woman here.

WANG ZENGCAI, Driver Instructor, Lhasa West Railway Station "I decided to stay in 2008, when I met my wife. I thought I might put down roots in Lhasa."

After marriage, they built a two-story house on the outskirts of Lhasa. From daily meals to home decor, traces of cultural blending can be seen everywhere.

WANG ZENGCAI, Driver Instructor, Lhasa West Railway Station "Xining in Qinghai, and Lhasa in Xizang, in my heart, both places are my homes."

Apart from people coming here for work, travellers from around the world also journey to Xizang by rail to experience its breathtaking landscapes. This is train Y831 from Xining to Lhasa, a tourist train packed with visitors from across the world.

ZHANG CHANGNING, Train Head, Y831 "It's a slow train, which makes it good for sightseeing. At Cuona Lake and Tanggula Mountains, it stops for more than 30 minutes."

Outside the windows, tourists take photos at the top of the world. Inside, songs about the "Sky Road" fill the air. For many travelers, this is a once-in-a-lifetime experience.

JIANG, Tourist from Hunan Province "I'm 65. I've always wanted to see the Potala Palace and travel this railway. It's a lifeline built by countless heroes."

TOURIST FROM CHINA'S TAIWAN REGION "I told myself back then that I would make this trip."

HASAN, Tourist from Indonesia "I truly admire the Chinese people. They built such a difficult railway."

JI YONGKUN, Tourist from Yunnan Province "This is the happiest road for all of us."

Since the Qinghai-Xizang Railway opened in 2006, more than 41 million passenger trips have been recorded into and out of Xizang. Passengers from around the world have taken the same "sky road" and crossed paths on the roof of the world. Wu Bin, CGTN, Lhasa, Xizang Autonomous Region.