During Pleistocene era (25,000 years ago), many regions of the world became raised and formed uplands. These regions are called Pleistocene uplands. In Bangladesh, Barendro region, Modhupur Gorh and Lalmai hills are parts of these uplands. The environmental characteristics and flora and fauna of these regions are almost similar. But the large area of Shaalbon is noticeable.
- Barendro: The region occupies the north-western region of Bangladesh including Chapainowabganj, Rajshahi, Nowgaon, Jaipurhat and part of Dinajpur. The total area of this region is about 9300 square kilometers and situated at about 6 -12 meters (20-40 feet) above sea level. In some area of this region the soil is terraced in steps.
- Modhupur Gorh: Modhupur Gorh includes Modhupur of Tangail district, Jamalpur, Gazipur, and parts of Dhaka and Narsingdi district. Total area of this land is about 4100-square kilometers and situated at about 15 -30 meters (50 -100 feet) above the sea level. Long ago there was a continuous Shaalbon of 160 kilometers long from Jamalpur to Dhaka. Now this forest is scattered into pieces. Though Chandra, Rajendrapur or Bhawal is treated as separate forests but they are actually parts of Modhupur forest. Brahmmaputra and Shitalalcchma rivers separate the eastern part of this forest from the main uplands. Egaro Sindhur, Shibpur, and Monohardi thana and part of Sonargaon are part of this separated region.
- Lalmai Hills: Lalmai Hills is situated near Comilla town and is about 14.5 kilometers (9 miles) in length and 0.8 -2.4 kilometers (0.5 -1.5 miles) in breadth. This is also a part of Pleistocene uplands. This hill is about 6 -12 meter (20 -40 feet) in height. Its highest pick is more than 46 meters (150 feet). Probably the name ‘Moinamoti Shaalbon Bihar’ originates because of the presence of Shaal forest here.