Lalmai Hills north-south elongated low hill range of about 17 km long and 1-2.4 km wide and about 8 km westward from Comilla Township is called the Lalmai-Mainamati hill range. The northern extremity of the hill ranges is at Ranir Bungalow whereas the southern extremity ends at Chandimura. The northern part of the hill range is locally known as Mainamati, while the southern part is known as Lalmai. The name Lalmai is probably derived from red soil or from the Lalambi forest (well known for medicinal herbs), close to devaparvata, the capital of the Devas of Samatat, was somewhere in the Mainamati hill.
The Lalmai hill area lies between the latitudes 23°20´N to 23°30´N and longitudes 91°05´E to 91°10´E. It covers an area of about 33 sq km. The hill ranges run through the middle of comilla district. The average height of the hills is about 15m but some peaks rise up to 45m or more. Most of the hilltops are capped by reddish-brown soil, which makes beautiful scenery of the hill range. These capping reddish-brown deposits are called Madhupur Formation of Pleistocene age. This Formation at Lalmai hill ranges is underlain by the dupi tila formation of Plio-Pleistocene age. The Madhupur and Dupi Tila Formations are separated by a gravel bed, which is called Quartz Chalcedony Gravel Bed. This boundary can be seen at Ranir Bungalow section. At the top of the Dupi Tila Formation, silicified woods can be seen at several places of the Lalmai ranges. Some of the hilltops represent table surfaces and deeply incised valleys separate the table surfaces from each other. It is assumed that these hill ranges are the continuation of the Arakan Yoma Hill Ranges. Probably, the Lalmai hills were uplifted in the Middle Pleistocene time during the final orogenic movement of the himalayas. The block upliftment of the hill ranges resulted table surface on some tops of the hills. Most of the ancient Buddhist monasteries are built on the tops of the hillocks of the Lalmai hill range.