Fangorn Forest:

The eastern remnant of the forests covering Middle-Earth in the Elder Days, Fangorn forest, and possibly the Old Forest, were the only remains of the forests of the Elder Days. Fangorn Forest was certainly the only one with the Shepherds of the Trees still surviving. Also called the Entwood, in Rohan, because of the Ents, who were the Shepherds of the Trees. Fangorn Forest was an obviously old forest, where there were some places that the original darkness still had not been lifted according to Treebeard.