This is an undeveloped spot good for bouldering / low-height roped climbing. I've walked by it a few times, but haven't jumped on the rock yet. It appears to be on public property abutting the sidewalk on the south side of 232nd Street in the Riverdale section of the bronx. Rock quality varies, and some assorted climbs exist. I can't imagine that this area could keep you entertained for more than an hour, but if you're in the neighborhood it's worth checking out.
Note that the base of this area is just a few feet from the road, so... although it's really just a bouldering spot (climbs between 10 and 20 feet), you may want to drop a rope.