Route 113, Madison, NH 03849
Largest known glacial erratic in New England, and among the largest in the world. A granite rock 83 feet long, 23 feet high (plus an additional 10-12 feet below ground), and 37 feet wide, weighing up to 5,000 tons! Designated a National Natural Landmark by the U.S. Department of the Interior in 1970. Madison Boulder Natural Area is unstaffed but is open to the public year 'round at no charge.