The preserve follows Buell Brook within the extensive Kilmer Woods at the north end of town. About 68 acres are within Highland Park itself. Paths like this follow the stream on into Piscataway near Livingston College. A great birding area.
The full Rutgers Ecological Preserve and Natural Teaching Area is 370 acres--68 in Highland Park, the rest in Piscataway and Edison. It contains "one of the finest old-growth forests of oak, ash, maple, and beech in central New Jersey," according to a Rutgers brochure. Old maps show that portion to have been uncut since at least the 1840s.
See Rutgers Ecological Preserve Map