In Puerto Rico, the iconic Arecibo Observatory, a radio telescope nestled into a giant crater, had to close after cables holding up a critical platform came crashing down. Experts analyze the cumulative effects that led to the collapse of this awe-inspiring structure.

On a snowy morning in Pittsburgh, a messy commute becomes dangerous after a bridge collapses; an investigation reveals how corrosion and other environmental factors helped bring down this decades-old structure.