GREEN BUILDINGS - A new approach to building sustainable urban environments are green buildings. Actually, this is an approach that might have been utilized to help cool one of the first cities in ancient times -- i.e. the hanging gardens of Babylon. Green buildings help reduce the "heat island effect" created by all the concrete of our urban areas that cause cities to be hotter than the surrounding area. This, in return, reduces the need for air-conditioning and energy usage. Green buildings also can help to absorb carbon dioxide from the air. Both can help reduce global warming. In this regard, there are several approaches to designing green buildings. One is to hang vegetation from the side of buildings. This is a particular attractive way to design parking garages to be more eco-friendly. For existing buildings, however, the preferred approach is to build green roofs. Not only can such green roofs reduce the heat of urban areas, but they also can catch and filter rain runoff, thus reducing the contaminated stormwater runoff that otherwise flows into our rivers and bays. In this regard, on Earth Day of 2009, the City of New York announced incentives and regulations to actually require the conversion of buildings to green roofs where there can be shown to be an economic benefit. Chicago is another city to aggressively promote the conversion of buildings to green roofs. What makes green roofs attractive today are new plastic membranes that are laid on the roof to collect the rain water run-off. A special soil is then put on top of the membrane in which plants are grown. The plants in turn absorb much of the rain water, thus reducing the stormwater runoff produced from the building. Above is an example of a green building built recently in Fukuoda, Japan.