Ring of Isengard

The Ring of Isengard were the rocky walls that surrounded and protected the Tower of Orthanc. They grew out of the wall of a valley at the southern end of the Misty Mountains, and were worked by the early Gondorians so that they formed a complete defensive circle around the tower. They were torn down by the Ents to make way for the Treegarth of Orthanc at the end of the Third Age.