Ludhiana is a city and a municipal corporation in Ludhiana district in the Indian state of Punjab. It is the largest city in Punjab, with an estimated population of 45 lacs. The population increases substantially during the crop harvesting season due to immigration of laborers from states like Uttar Pradesh, Bihar and Delhi. It has an area of about 310 km�. The city stands on the Sutlej River's old bank, 13 km south of its present course. It is a major industrial center of northern India. Ludhiana is centrally located on the National Highway 1 from Delhi to Amritsar, and is connected to the Indian capital city of New Delhi by road and frequent train service. Ludhiana is the richest district in the state of Punjab, and also includes the most expensive fertile land of all of India. Ludhiana district is considered to be one of the NRI hubs of Punjab.