In what could have been a nightmare come true, part of the glass floor in a viewing box high above Chicago cracked right below a group of California tourists. But it was apparently much less of a problem than it might have seemed.

Alejandro Garibay and his family were taking in the sights at Chicago's Willis Tower on Wednesday night. The tower's Skydeck, which opened in 2009, is on the 103rd floor, about 1,353 feet above Chicago's downtown.

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"When we pulled our phones to start recording and take pictures they asked us to leave right away," Garibay said.

A building spokesperson told the Chicago Sun-Times that it was the protective coating that cracked.

“Occasionally this happens, but that’s because we designed it this way,” he said. “Whatever happened last night is a result of the protective coating doing what it’s designed to."