The High Line, a hairline of greenery running 22 blocks atop a nearly forgotten railroad viaduct, has improbably become a global phenomenon. Threading its way between factories tangled with water tanks and fire escapes, the dilapidated viaduct was turned into a park in 2009 and now attracts human traffic jams. A neighbor has put on coy fire-escape performances. I hear that guests in a hotel that looms above the park sometimes undress for the pleasure of the strolling throngs. Tomorrow, the second stage of the $153-million park opens, stretching 10 blocks from 20th Street in Manhattan’s West Chelsea, to 30th Street -- more than doubling the length of the first phase. Last week, I walked the new stretch with two of the park’s designers, Ricardo Scofidio, a principal at the architecture firm of Diller Scofidio and Renfro, and James Corner, the landscape architect, who is principal of James Corner Field Operations. Curious folks pressed noses against the dividing chain link fence that is about to come down. Corner smiled, remembering when his client -- the nonprofit Friends of the High Line -- worried no one would come. Read more at Bloomberg. ____________________ James S. Russell is the architecture columnist for Bloomberg News. He has written about cities, architecture, and environmental design for more than 20 years. His new book is The Agile City: Building Well-Being and Wealth in an Era of Climate Change.