The Purple Mountain Group is bounded to the west by the Gap of Dunloe, which separates it from MacGillycuddy's Reeks range. To the south and east are the Lakes of Killarney and to the north is the wide, flat valley of the River Laune. The eastern half of Purple Mountain is part of Killarney National Park. Within the national park, the lower slopes are covered in oak forests, some of which are remnants of those that covered Ireland before the arrival of humans.