The Kalka–Shimla Railway is a 2 ft 6 in (762 mm) narrow gauge railway in North-West India travelling along a mostly mountainous route from Kalka to Shimla. It is known for breathtaking views of the hills and surrounding villages. Spectacular scenery along the whole route, and the marvels of its construction, keeps the traveler on this line spell bound.
On leaving Kalka, 656 meters (2,152 ft) above sea level, the railway enters the foothills and immediately commences its climb. The route offers a panoramic feast of the picturesque Himalayas from the Sivalik foot hills at Kalka to several important points such as Dharampur, Solan, Kandaghat, Taradevi, Barog, Salogra, Summerhill and Shimla at an altitude of 2,076 meters (6,811 ft).
The Kalka–Shimla Railway runs through 103 tunnels (one is not in use; so only 102 in service). The longest tunnel Barog, and is associated with local tales and legends related to its realization. The line has 864 bridges, one of which is a 18.29 metre (60 ft) plate girder span and steel truss. The others are viaducts with multi-arched galleries like the ancient Roman aqueducts. Bridge No. 493, historically known as the "Arch Gallery", situated between Kandaghat and Kanoh stations, is an arch bridge in three stages, constructed with stone masonry. Bridge No. 226; between Sonwara and Dharampur is an arch gallery bridge having 5 tier galleries of multiple spans, constructed with stone masonry and bridging a deep valley surrounded by high peaks.