On a hilltop in Yunnan province, campers can frequently hear the whistles and humming of train engines, as trains slowly make their way through the mountainous terrain on the narrow-gauge tracks.

The trains still run on the tracks of the Yunnan-Vietnam Railway, which was built over 114 years ago. There is no other railway like this, as it is the only 1-meter-gauge railway still in operation in the Chinese mainland. Described as a wonder of the Industrial Age, an increasing number of visitors have been drawn to the railway's history and many want to embark on the journey through time by hiking along the mustard-colored French-style stations.

The 854-kilometer-long Yunnan-Vietnam Railway connects Yunnan's capital Kunming with Vietnam's port city Haiphong. Backed by French capital and technology, construction of the Chinese part of the railway measuring 465 km started in October 1903 to facilitate France's colonial trade. But due to numerous difficulties in the project, many Chinese workers lost their lives.

After it began operations on March 31, 1910, The Times, a newspaper in the United Kingdom, named it one of the "Three Engineering Marvels of the World", along with the Suez Canal and Panama Canal.

In February 1958, the Chinese section of the railway was named the Kunming-Hekou Railway. To this day, it still conducts freight services between China and Vietnam daily.