What is the zoning like in Manhattan? I see intermingled residential/office/commercial spaces everywhere I go (heck, my last office was in the same building as apartments, with a store-turned-restaurant on the ground floor), so I didn't realize there were zoning restrictions in that sense.
there are crippling height restrictions all over the place, and you have to buy un-used "air rights" from your neighbors to build anything taller than what already exists in the neighborhood
environmental impact studies (weirdly) can be used against projects
local "community boards" have a lot of power
and the aforementioned centrally imposed limits on development -- the city's top-level boards may not like what you're doing to transportation
