The problem I have is most cities have plenty of green parks already. In a few places they could use a new park, but in general there are far more parking lots (often 50% of a city is parking lot!) than there is need for green space. Much better is tear up a parking lot and replace it with a building that lets people do something in the city other than pretend they are in a rural area. Nothing wrong with rural areas and parks, but there is more to life than those. Put in more apartments, offices, restaurants, opera houses - all those other things that make a city great.