About ½ mile north of Exit 1 (northbound access only) of the Palisades Interstate Parkway.
One can see the George Washington Bridge to the south. Beyond the lookout are the walls and other foundation remains that were once part of the arch-windowed estate of Dr. Ernest Cadgene (early 1900s and demolished in 1941).
John Rockefeller acquired many of the estates that once lined the top of the Palisades cliffs. In 1933 he donated them to the Palisades Park Commission but stipulated that a scenic parkway had to be built from the GW Bridge to Bear Mountain and that all the estates had to be torn down. One of the estates not owned by Rockefeller was the Penlyn Estate (owned by Herbert Oltman), which became the park headquarters.)
(Source: THE NJ PALISADES: http://www.gpswnj.com/abandon/nongps.html)