'The ledge' opens at the Sears Tower in Chicago

Children look down the glass floor of 'the ledge' Photograph: Frank Polich/Reuters

A photographer snaps a picture while standing on the ledge”. The set of glass balconies is now open to the public Photograph: Frank Polich/Reuters

A girl looks down on Chicago from the Sears Tower. The structure is the tallest building in America Photograph: Kamil Krzaczynski/EPA

Five-year-old Anna Kane, left, and Sophie Allaway, 4, peek through the glass floor of the ledge. Sears Tower officials say the inspiration for the balconies came from the hundreds of forehead prints visitors left behind on Skydeck windows every week Photograph: Frank Polich/Reuters

Photographers take snaps from "the ledge” Photograph: Frank Polich/Reuters

Sam Kane lays on the glass floor of the ledge.” The glass includes three layers, each 1.3cms thick Photograph: Scott Olson/Getty

Visitors walk out on the “ledge” at Sears Tower. The skyscraper is 110-storeys high Photograph: Getty