 The mine comprises nineteen stories , of which eleven are below ground . From the entrance , the mine extends about 730 meters ( 2440 ft ) into the mountains , and the total length of its tunnels is about 40 km ( 25 miles ) . Quarrying is done using the room and pillar method , mining only half of the salt and leaving the remaining half to support what is above . The temperature inside the mine remains about 18 – 20 ° C throughout the year . A 2 ft ( 610 mm ) narrow gauge railway track laid during the British era is used to bring salt out of the mine in rail cars . 
