As Munnar does not have a railway station, you will have to travel to the nearest station, Aluva. This is around 110 kilometers from this city. You can also travel to Ernakulam, that is around 130 kilometers away. If you are traveling to this station, you can get down at either Ernakulam Town (North) or Ernakulam Junction (South). This is one of the major railway stations of Kerala and is considered one of the A1 graded stations in the Southern Railways.
The other closest station is Madurai which is about 135 kilometers away. These stations are all operated by the Southern Railway zone of the Indian Railways and falls under the arena of the Thiruvananthapuram railway division. You can always take a taxi from these stations till Munnar for around 2500 rupees. Book a pre-paid taxi or cab well in advance to avoid any hassles when you reach here.