The famous Skydeck of the Willis Tower — which features a set of transparent ledges situated more than 1,300 feet in the air and extending 4.5 feet out from the skyscraper — experienced what appeared to be cracks in one of its boxes on Wednesday, alarming tourists who had come to the attraction for its aerial views of Chicago.
Cracks seemed to appear in parts of the floor of a ledge box on Wednesday evening. The fissures appeared beneath tourists' feet in the structure's floor, which provides a transparent view of the 102 stories below.
Officials at the Willis Tower said the cracking was in a scratch-resistant coating on the glass structure and did not affect the structural integrity of the box. "The protective coating on the glass cracked in one section, but the glass itself did not," they said on Twitter.
A report from a local NBC affiliate in Chicago stated that a family heard the cracking after they stepped out on the ledge at around 9:50 p.m. Wednesday.
The Skydeck remains open to the public as of Thursday, but four of its ledge boxes have been closed for "routine inspection," officials said via Twitter. They said the coating on the affected ledge box is being replaced.
The Willis Tower — formerly known as the Sears Tower — is among the tallest buildings in the U.S. and is a popular tourist attraction in Chicago. The ledges at the Skydeck first opened in 2009.