The Gap of Dunloe is not a road that was built so much as a channel that was left behind. Ice did the engineering. During the last glaciation, a tongue of ice ground south-east between Macgillycuddy's Reeks and the Purple Mountain range, scouring an eleven-kilometre defile through Old Red Sandstone. When the ice withdrew, it left a chain of five small lakes — Coosaun Lough, Black Lake, Cushnavally, Auger and Black Lough — strung along the floor like beads on a wire. The Gap of Dunloe bike and boat tour follows that glacial line almost exactly. The Irish name, Bearna an Choimín, means the gap of the common land. That phrase carries its own history. For centuries this was shared grazing, worked by tenant families whose stone field walls still climb the lower slopes at angles no modern farmer would attempt. The Wishing Bridge, roughly halfway along the pass, dates to the nineteenth century and takes its name from a local belief that wishes made upon it are granted. Kate Kearney's Cottage stands at the northern entrance. Kate Kearney herself was a real woman who sold illicit poitín to travellers in the 1840s, before the Famine emptied much of the valley. What makes the place matter now is that it was never tamed. The pass remains a single-track public road with no barriers, no lighting and no widening. Killarney National Park, established in 1932 and designated a UNESCO Biosphere Reserve in 1982, wraps around its southern end. Red deer — Ireland's only continuous native herd — graze the Black Valley beyond Lord Brandon's Cottage. Sessile oak woodland at Derrycunnihy is among the last unbroken temperate rainforest in the country. South of the pass, the landscape opens into the Black Valley and then the three Lakes of Killarney: Upper Lake, Muckross Lake and Lough Leane. The Old Weir Bridge at the Meeting of the Waters is a two-arched stone crossing where oarsmen still shoot the rapids by hand, a technique unchanged in two hundred years. Innisfallen Island, in Lough Leane, holds a monastery founded around 640 AD whose annals record four centuries of Irish history. Ross Castle, a fifteenth-century O'Donoghue tower house, marks the landing point. Entry to the pass itself costs 0 EUR — the Gap is a public road, open to walkers and cyclists at any hour. The Gap of Dunloe bike and boat tour simply adds a boat at the far end, turning a there-and-back climb into a one-way crossing of an entire glaciated valley system.