Which natural features made the early Calcutta site difficult to live in?

The early site of Calcutta (now Kolkata) was considered difficult to inhabit primarily due to its challenging natural topography. The area was characterized by a low, swampy, hot, and humid riverbank that made the environment unhealthy.12

Specifically, the region featured extensive marshes to the east and various swamps within the immediate area, which contributed to the site being described as a pestilential town in its early years. Because the land sloped away from the Hugli (Hooghly) River toward these marshes and swamplands, the terrain was naturally prone to these conditions. These environmental factors necessitated significant efforts in later years to raise and drain the ground, particularly in the areas where the British sector was eventually constructed.132