A protected landscape, Gajna is a typical Slavonian Sava valley pasture with abundant swamp animal and plant life situated east of Slavonski Brod close to the villages of Oprisavci i Poljanci. It has several alluvial depressions that are filled with water during spring and autumn floods thus enabling regeneration of the swamp flora and fauna.
This landscape represents a unique example in Croatian of positive impacts of human influence on the environment, which has not only ensured supply of fresh water for cattle watering but has facilitated development of wildlife.