Minecraft wiki entry for Rain_Forest, associated text: Rain forests were a lush biome which existed in the game prior to the first part of the Adventure Update. They can be viewed as a forerunner to the jungle biome seen in later versions of Minecraft, due to their denser-than-average vegetation, higher oak and birch tree concentration and more common large oak trees. They usually consist of low flat plains and high cliffs and hills but can be very mountainous.