Rabindra Sarobar Lake, previously known as Dhakuria Lake, is an artificial lake in south Kolkata. This is Kolkata’s only national lake is spread over 48 hectares and comprises several smaller water bodies. It was dug in 1920s to provide soil for filling up the low-lying areas of Ballygunge, which was at that time being made habitable by the Calcutta Improvement Trust. It is popularly referred to as the "Lungs of Calcutta".  The lake is suffering from environmental degradation. Water pollution is on the rise, owing to encroachment. Rabindra Sarobar has shrunk beyond recognition and its water is heavily polluted as large numbers of people are using its water for washing and bathing purposes, daily.