Beaver Brook Falls is a literal hidden gem. Its double plunge 12-foot cascade is tucked behind boulders and covered with a canopy of trees. It’s a refreshing summer respite as the falls drop into a small swimming hole inside “Beaver Brook Canyon.” There isn’t an official trail to the base of the falls and the swimming hole, though there is a noticeable short and steep trail about 20 feet beyond the canyon marker sign. Getting there is a cinch. Take a stroll along the old Route 9 where nature has reclaimed the road. It is an easy walk of about 3/4 of a mile each way past the gate to an outlook with a view from the top of falls. The babbling Beaver Brook follows the entire path with many places to catch a glimpse of mini cascades. Several large rock formations line the sides of the path and about a half mile up on the left is the most prominent of all, “Old Man of Keene.” The path continues past the falls for about a 1/3 mile after the broken pavement becomes a double track dirt pathway. Beyond the falls there are a few short side trails leading to the brook. This is probably the most accessible must-see natural feature in the Monadnock region.
Most authoritative ( Keene Parks and Recreation manages the area, but has no info on it): https://ci.keene.nh.us/parks-recreation