Please note that this route follows an unpaved trail.
Follow the Old Croton Aqueduct Trail (OCA) back to its source. Take Metro North railroad back to the city. Or find your way back via the County Trailways (sorry, no directions to it printed here, yet.)
The OCA is a rough trail, unpaved except in places. If you don't like what you have found you can always look for the nearest Metro North Hudson Line station to return. And that is one of the beauties of this route. You can do it off-season or in questionable weather, knowing you have nearby rail access for a bailout along the route.
Ken has added viewpoints and resources along the route. Check the RWGPS map for these icons. Here are Ken's original notes:
A few more links:
The OCA Trail Map:
OCA State Park:
Croton Aqueduct Wiki: