The Brooklyn Botanic Garden has long been a leading advocate of urban greening and sustainable design--and a green roof is an exciting expression of these ideals. Vegetated roof systems prevent water pollution, cool and purify the surrounding air, extend roof life, and improve energy efficiency. Here are 13 of New York City's most remarkable examples--including the elevated lawn at Lincoln Center--along with a detailed historical overview, essays by industry experts, and practical advice readers can use to turn their own roofs green.