Even a hangover couldn’t spoil the beauty of the photos from last night. Katie lay on the couch, legs dangling over the end, scrolling through them. She and Alex had gone to a rooftop bar that not only boasted glittering, magnificent drinks with names like “Hibiscus Heaven” and “Lavender Lemonade,” but bloomed with walls upon walls of vertical gardens that were bursting with flowers of every shape, size, and color. The hanging gardens , she thought when she first saw them.  O