The Darjeeling Himalayan Railway is remarkable not only because of its age and mountain scenery but also because of the extremely narrow railway track on which it operates.
Its gauge is only 610 millimetres, or 2 feet.
The railway extends for approximately 88.48 kilometres between New Jalpaiguri and Darjeeling.
Engineers used innovative solutions including zigzag reverses and loops to enable trains to gain elevation through the Himalayan foothills.
The railway opened in 1881 and was inscribed on the UNESCO World Heritage List in 1999.
Its tiny gauge and challenging route make it one of India's most distinctive operational railway systems.