History's most fatal engineering flaw. On the night of July 17, 1981, just seconds after witnesses heard a sound "like a tree limb cracking," two massive skywalks inside Kansas City's Hyatt Regency hotel tore loose and crashed into a crowded lobby, killing 114 people and injuring more than 200. It's still the deadliest structural collapse in U.S. history, and a horrifying example of one tiny design change leading to a total catastrophe. Today, engineering schools still teach the case as a stark reminder of how the smallest details carry the largest weight.
The codebreakers who unraveled the Soviet spy network. In 1943, a 22-year-old teacher named Gene Grabeel arrived at a mysterious Army facility outside Washington, where she was given drawers full of meaningless five-digit numbers and asked to sort them. Though she didn't know it at the time, turns out those numbers were Soviet intelligence cables protected by a cipher thought to be mathematically unbreakable. She and her colleagues would eventually crack open the Venona project—and pull off perhaps the biggest counter-espionage breakthrough of the Cold War.
