Darjeeling Himalayan Railway(DHR),built in the late 19th century, was something of a technological marvel.
The DHR is a preserved narrow-gauge (2ft or 610mm) railway based on zig-zag and loop-line technology.
It runs between New Jalpaiguri and Darjeeling in West Bengal.
Built between 1879 and 1881,the DHR is about 88 km with six zig-zags and five loops.
Its track rose from the sea level, the elevation varying from about 328 ft at New Jalpaiguri to about 7,128 ft at Darjeeling.
UNESCO declared the DHR or Toy Train, a World Heritage Site on 2nd December 1999.