Four great forests (arañña) are often mentioned in literature (e.g., M.i.378). They had once been the sites of very populous and prosperous kingdoms, but had later been destroyed by the gods because of offences committed by their kings against holy men.
The four great forests are: Daṇḍakarañña, Kāliṅgarañña, Mejjharañña, and Mātaṅgarañña.
Details of these are found under each respective name.