Kolkata (Bengali: কলকাতা / কোলকাতা) , formerly Calcutta , is the capital of the Indian state of West Bengal. Located on the east bank of the Hooghly river, it is the principal commercial, cultural, and educational centre of East India, while the Port of Kolkata is India's oldest operating port and its sole major riverine port. , the city had 4.5 million residents; the urban agglomeration, which comprises the city and its suburbs, was home to approximately 14.1 million, making it the third-most populous metropolitan area in India. , its gross domestic product (adjusted for purchasing power parity) was estimated to be 104 billion, which would be third highest among Indian cities, behind Mumbai and Delhi. As a growing metropolitan city in a developing country, Kolkata confronts substantial urban pollution, traffic congestion, poverty, overpopulation, and other logistic and socioeconomic problems.