An intensive rooftop is another kind of green roof. This is more of an elevated park that has been cultivated as any regular park might. According to Discovery, intensive green rooftops “can sustain shrubs, trees, walkways and benches with their complex structural support, irrigation, drainage and root protection layers. The foot or more of growing medium needed for an intensive green roof creates a load of 80-150 pounds (36-68 kilograms) per square foot.” Pictured here is Chicago’s award-winning City Hall green rooftop, which combines extensive, intensive and semi-intensive traits. Chicago’s 20,300-square-foot City Hall contains more than 20,000 herbaceous plants installed as plugs, including 100 woody shrubs, 40 vines and two trees: a Cockspur hawthorn and prairie crabapple.”