Listed on some maps as Whippoorwill Ridge Park, this area was formally declared a nature preserve by the Town of North Castle under the name of Betsy C. Sluder Nature Preserve and includes 70 acres of trails, ponds, rock formations, and one of the Leatherman caves.
I originally scouted the park a couple of days before Hurricane Irene. In the aftermath there are a lot of downed trees and some flooded areas. None should pose a problem for hiking, but I've upped the terrain rating until some park clean-up occurs in the future.
The main parking lot is off Old Route 22 in Armonk. A small lot with room for 3 cars can be found up a shared driveway on Shippen Road. The first stage is small, the final is an ammo box. You can make a nice loop walk by taking the red trail down to green and around or vice-versa.
There is a clue taped in the lid, and also found in the log book that will lead to the Go Fish (visit link) mystery cache.