Four men had a terrifying few moments when the glass floor they were standing on 103 stories above Chicago in the Willis Tower observation deck appeared to develop cracks.
The men were standing in one of the tower's glass boxes that extend out about 4 feet (1 meter) from the observation floor on Wednesday night when a protective coating on the floor shattered, building spokesman Bill Utter said.
The men were never in danger, he said.
The Willis Tower, previously named the Sears Tower, is one of the tallest buildings in the United States and was once the tallest building in the world.
The floor began to crack when Alejandro Garibay, two of his cousins and his brother stood up after sitting in a box to pose for pictures, Garibay wrote on his Facebook page.
"One of the craziest feeling(s) of my life," wrote Garibay, who is from Stockton, California.
Utter said the coating protects the glass so that visitors have a clear view 1,353 feet (412 meters) to the ground. The boxes make up the Ledge, a popular attraction.
"At no time was the integrity of the Ledge in doubt," Utter said, adding that the protective coating in the boxes breaks occasionally.
(Reporting by Brendan O'Brien; Editing by Jonathan Oatis)