A drive of 11 kilometers or so takes visitors up through the scenic Gap of Dunloe, a majestic narrow mountain pass carved by glacial ice. This rocky pass separates Purple Mountain and its northern foothills in the western part of Killarney National Park from Macgillicuddy's Reeks and is so outstanding, you'll remember it forever. The gap is best reached from the R562, which follows the north side of the Lower Lake. From the road to the Gap, visitors can see Dunloe Castle, tucked in a grove…