Black Rock Forest. This conservancy used to be an experimental forest owned by Harvard but is now open to the general public. It's in the same vicinity as West Point, a little north of Harriman State Park.
We got there via bus to Highland Falls (query: why does it cost more to travel an hour north than it does to take the bus to Philly?), but the trail isn't right on any route, so we had to hike through the streets, past the freeway, to get to the trail proper. Most of the hike was on roads, in fact - but old dirt roads in the forest.
The forest has half a dozen ponds, all but one of which are used as reservoirs. We stopped to swim in Sutherland Pond, the sole exception. The weather had lightened up enough to make swimming pleasant; the morning had been overcast, and the forecast called for afternoon thunderstorms. Thankfully, those didn't materialize.
The hike totaled nearly 13 miles. It was a pleasant hike with a few nice views, typical scenery from what I am beginning to understand of the area.