The famed Hanging Gardens of Babylon have been claimed in recent years to be the first known examples of green roofing. Or maybe they can be classed as the earliest attempts at hydroponics. Although they found fame as one of the Seven Wonders of the World there is one problem: They may never have existed. At least, not built be Nebuchadnezzar who ruled his city-state of Babylon 605-562 B.C.