This is where the tower of Orthanc resides. It is where everything to do with war is done. And considering everything to do with the Urukai is war..... it is very important. On the borders of the Orthanc walls is the fangorn forest. It is an even bigger forst than Lorien.
Once the Ents where against Isengard. Now that they have dwindled to nearly nothing, the remaining 2 ents have given in and do not defend fangorn at all.