One of the tallest skyscrapers in New York doesn't look like it should be standing — and for a brief time, there was a chance that it wouldn't. 601 Lexington, formerly known as the Citigroup Center, stands on a pair of over 100-foot-high stilts that originally allowed it to be constructed around a church occupying the land. It's a striking and inventive design, but as 99% Invisible reports, it wasn't perfect: a year after its construction in 1977, engineers realized that just the right type of wind could make the entire building blow over, and there was a one in sixteen chance of that happening each year. Head over to 99% Invisible for details on how the building was repaired in secret, without anyone finding out about the potential danger until 1995.