on Ferry Road, which involves the railroad crossing, historic properties, eminent domain, DOT, protected wetlands, etc, etc. (For the moment it seems "lack of funding" has spared beautiful Ferry Road, but who knows--- if the economy turns around it could be threatened again.)
I've always used the (hard-to-find) unmarked wooded trail off Ferry Road to get to the ice house (look for the cut log along the right side of the road); today I realized there is also "Ice House Road" (duh) just to the north, which isn't as adventurous, but has much less poison ivy.
(can you see the ice house in this pic? It's there!)
Both trails are kind of magical, but the southern one is longer and winding and wooded and hilly, and follows the river's edge right before you get to the ice house ---- then the ice house takes you by surprise when you sort of stumble on it suddenly, and it towers over you.
Unfortunately, they put black chain-link fencing in all the window openings,
which diminishes the appeal of the ruin pretty significantly, but
the patch of land on the north side of the building is kept mowed and there are two picnic tables right near the river's edge, so it's an ideal spot for a quiet lunch
(bring a plastic tablecloth; the tables don't get enough sun and are rotting). It's also very likely you'll have the whole place to yourself, I don't think it gets a lot of visitors.
Here's a google earth shot of Nutten Hooke---the ruin is in the woods at the left. Plenty of parking at the end of Ferry Road, where you can also launch a kayak or just take in the wide, wonderful Hudson River views.