 The Khewra Salt Mine ( or Mayo Salt Mine ) is located in Khewra , north of Pind Dadan Khan , an administrative subdivision of Jhelum District , Punjab Region , Pakistan , which rises from the Indo @-@ Gangetic Plain . It is Pakistan 's largest and oldest salt mine and the world 's second largest . It is a major tourist attraction , drawing up to 250 @,@ 000 visitors a year . Its history dates back to its discovery by Alexander 's troops in 320 BC , but it started trading in the Mughal era . The main tunnel at ground level was developed by Dr. H. Warth , a mining engineer , in 1872 during British rule . After independence , the Pakistan Mineral Development Corporation took over the mine , which still remains the largest source of salt in the country , producing more than 350 @,@ 000 tons per annum of about 99 % pure halite . Estimates of the reserves of salt in the mine vary from 82 million tons to 600 million tons . 
