Kolkata is located in the eastern part of India. It has spread linearly along the banks of the Hooghly River. The Kolkata Municipal Corporation has an area of 185 square kilometres. The city is near sea level, with the average elevation being 17 feet. The whole area is in the Ganges Delta and is monotonously plain. The Bay of Bengal coastline is about 60 miles to the south. The Sundarbans National Park starts within 100 km south to the city. Most of the city was originally marshy wetlands, remnants of which can still be found especially towards the eastern parts of the city where the remaining wetlands have been converted to fish farming centres. Human habitation has led to the establishment of mature trees and shrubs. The original marshland has been changed to a primarily moist deciduous habitat which flourishes under the high rainfall and sunny humid climate.