The Lost River Gorge & Boulder Caves, located in New Hampshire’s Kinsman Notch in the White Mountains, is a series of boulder caves surrounded by flowing water. The Ice Age brought glaciers more than a mile thick to this area 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. The first documented exploration of Lost River took place in 1852. When the Jackman brothers, Royal and Lyman, were fishing along the stream the boys worked their way over and around the boulders when suddenly Lyman disappeared out of sight. Lyman had slipped into a moss covered hole and fallen into a cave about 15 feet below into a pool of water about waist deep. Now known as Shadow Cave, it was the first of the many caves the boys would soon discover.