PHOTO: Credit – Andrew Seng for The New York Times

The Cooper Street Rock, in Upper Manhattan, sat undisturbed for millenniums. Now it’s on the market — or at least half of it is.

It is one thing to try to sell a 30,000 cubic foot rock in a hot real estate market; it’s another thing entirely to try to sell half of one.

That is precisely what is happening on a stretch in Inwood, the recently rezoned neighborhood in northwest Manhattan. It is there that an investor named Ilan Tavor is trying to sell a vacant lot for close to $3 million — a lot that consists entirely of a 30-foot-tall mound of bedrock.

That in and of itself might not be so odd — the new zoning allows a potential developer close to 20,000 buildable square feet. But Mr. Tavor’s company, Cooper Development LLC, owns only the southern half of the rock. The northern half is owned by a cooperative apartment building, 60 Cooper Street, which, in a quirk of New York real estate, isn’t actually next to the co-op. Its half is on the other side of Mr. Tavor’s lot.