Straddling the equator, the largest and most landlocked of the Congo departments.
Low relief.
Types of plant formations: marshy or flood-prone forests and grassy meadows.
Equatorial climate, hot and humid.
Temperatures oscillating between 24 and 30 ° C and rains, abundant and regular, between 1600 and 2000 mm per year. With two peaks, in May and October
Short dry season, from December to March
Two major rivers: the Oubangui and the Likouala-aux-herbes with two tributaries: Ibabga and Motaba