The city owns the building. That's what happens when you build on land not your own. This is true everywhere. If you build a building in New York City, on city property (which is common), the building belongs to the city unless you have a iron clad contract that says otherwise. In the absence of such a contract, the city gains ownership of the building. NYC won't sign off on such a contract without dozens of defaults stipulated in which the building owner can default and lose the building. Ask Donald Trump. He has a story to tell on this one.