Bosco Verticale

Bosco Verticale in Milan turns out to be a forest wearing a skyscraper as a disguise: every balcony across its twin towers holds a real tree, part of a planting that runs to more than seven hundred trees and thousands of smaller plants across ninety species. The guide follows the professional arborists who abseil down the towers' faces every few months to tend it, and architect Stefano Boeri, who has said the idea partly grew out of an Italo Calvino novel about a baron who climbs into the trees and never comes back down. Engineers ran wind tunnel tests before construction so a storm off the Alps would not tear a tree loose over the street below. Look up and count the balconies as you listen, each one anchoring a tree in a concrete tub deep enough to hold it against the wind.