Pyramid Mountain Natural Historic Area Boonton Avenue, Kinnelon, NJ07405 Pyramid Mountain Natural Historic Area is more than 1,500 acres and hometown to the well-known Tripod Rock. Tripod Rock…More is a 160-lb. boulder that sits on top of three smaller rocks. Many theories have been made about how the huge boulder was placed on the smaller rocks and how it has remained in place for many years. Pyramid Mountain features several marked trails, streams, ponds and fields. Biking is not allowed on the trails.