To find this cache, take the middle path through the barberry once you cross the bridge. Proceed up a steeply ascending dirt trail until it loops sharply to the right. At that point, pick out a path from the rocky hill (over a downed tree) up to the very top. You'll be rewarded with this cache and a fabulous view of Storm King Mountain. During weekends with nice weather, this can be a high muggle area.
The park is just north of Cold Spring village, within walking distance of the Metro North Train Station.