The Lost River Gorge & Boulder Caves, located in New Hampshire’s Kinsman Notch in the White Mountains, is a land of spectacular beauty forged by the powerful forces of water, wind, weather, and time. The shaping of Kinsman Notch and the surrounding mountains began about 300 million years ago. The Ice Age brought glaciers more than a mile thick that grounded, lifted, and deposited rocks that formed notches and mountains. When the ice melted, the water carried debris, eroding the rocks and forming Lost River Gorge. Lost River is so-named because the brook draining from the south east part of Kinsman Notch disappears below the surface in the narrow, steep-walled glacial gorge. The Gorge is partially filled with immense blocks of granite, through which the brook cascades along its subterranean course until it eventually emerges and joins the Pemigewasset River, which flows south from Franconia Notch.