The Bamboo Forest is, as its name suggests, a vast forest of bamboo. Many bamboo forests were mentioned in the Kung Fu Panda franchise—among one was specifically given this name in Secrets of the Masters, when Oogway was escorting Rhino, Ox, and Croc to Wu Fortress to defeat the Wu Sisters.
The Bamboo Forest is a forest entirely of green bamboo. During their trek across the top of the bamboo shoots, Croc noted that he could see his swamp from where he was, suggesting that the forest is quite close to it.
After encouraging Rhino, Ox, and Croc to work together in stopping the Wu Sisters, Oogway escorted the trio to Hubei Volcano where the sisters' fortress was located. They navigated through a bamboo forest along the way, climbing and hopping among the top of the bamboo shoots to cover more ground.