The Lost River Reservation (also known as the Lost River Gorge & Boulder Caves) is a protected area with a series of caves along a gorge in the White Mountains in Woodstock, New Hampshire, United States. Located west of the village of North Woodstock on New Hampshire Route 112, Lost River Reservation is set in Kinsman Notch. One of the White Mountains' major passes, Kinsman Notch lies between Mount Moosilauke and Kinsman Ridge at just under above sea level.