The northern section of the Air Line Trail is particularly captivating, featuring an old bridge and the intriguing "Hermit Cave," and culminating at the tri-point marker where Connecticut, Massachusetts, and Rhode Island meet. This boundary is identified by a 4-foot granite monument (with an additional 5 feet underground) situated in a small hilltop clearing. The marker, 14 inches square with a 6-inch pyramidal top, is inscribed with "MASS 1883" on the north side, "R.I. 1883" on the south, and "CONN" on the west—Connecticut's side lacks a date due to disagreements over the boundary. This monument was installed by a commission from Massachusetts and Rhode Island in late 1883.