The train line to Lhasa has rewritten many of the world's records for extreme engineering. It's the world's highest railway, with more than 966 km (600 miles) of track above 13,000 feet, reaching above 16,500 feet in several locations. The line is also home to the world's highest railway station, which at Tangu-la Pass sits at almost 17,000 feet.
The train is comfortable and inexpensive, with free oxygen supplies beneath every seat to combat altitude sickness. Traveling by rail is also the perfect way to see the vast uninhabited expanse of the northern Qinghai-Tibet Plateau, with yaks and antelopes roaming the hills.