Lovely trail section of the Baldpate trail system, recently re-blazed with drainage improvements. Less steep than Summit or Switchback trails, but lovely in its own right. We suggest loop hike: Kusar Mountain to Copper Hill (either branch, western harder and wetter), to parking lot, then return via Kusar Mountain, which starts near high tension wires.
In recent years, Princeton has gotten serious about preserving open space. Recently, Princeton added Witherspoon Woods to its park system and trail network. It’s only 40 acres, but it adds charming terrain and a slightly more challenging way to access the Mountain Lakes Preserve. I stumbled upon it by accident and fell in love with it. A wonderful introduction to “real hiking” for beginners, and a charming walk for everyone. (Driving time is about 25 minutes. Rated Beginner though the footing is rocky in places and can get muddy in wet season)
Just north of Mercer-Hunterdon County line is the Dry Run Creek trailhead, 20 minutes or so north of downtown Trenton by car. Maintained by the D&R Greenway Land Trust, it’s a delightful, 1.2 mile trail that descends into Dry Run Creek* and then climbs about 230 feet to 518 and another parking lot. There, if you look directly across the road, you can continue on the Rockhopper Trail. Altogether, you can walk an entertaining 10+ mile round trip hike.