The Kolkata Metro or Calcutta Metro is a metro system serving the city of Kolkata and the districts of South 24 Parganas and North 24 Parganas in the Indian state of West Bengal.
It is the first underground metro railway system in India. The network consists of one operational line (Line 1) and one under construction (Line 2), with four further lines in various stages of planning. It was the first such form of transport in India, opening for commercial services in 1984.

Source: http://en.wikipedia.org/wiki/Kolkata_Metro