Tragedy struck Puerto Rico in November 1996 when a propane gas explosion collapsed a six-story tower with the popular Humberto Vidal shoe store on the first floor. The disaster killed 33 people and wounded more than 80 others.

A sinkhole engulfs a Bronx residential street, growing so large that it swallows a van. Experts explain how heavy rain and old infrastructure caused this terrifying calamity.

Twenty people are killed in Fremont, Nebraska, when the Pathfinder Hotel explodes on the cold Saturday morning of January 10, 1976. An investigation into the tragic gas leak leads underground to where gas lines supply this iconic building in America's heartland.

In Scotland, a distinguished library is ravaged by not one but two disastrous fires; experts explore how outdated construction methods and materials contributed to the vulnerability of this esteemed place of learning.

An aging dam in Nebraska is overcome by flooding after the area is hit with a devastating bomb cyclone; an investigation reveals that massive chunks of ice unleashed by the superstorm played a critical role in the failure of the old 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.

A crane collapse at a high-rise construction project in March 2008 left seven dead on a Saint Patrick's Day holiday weekend in Manhattan. An investigation reveals how a shortcut used while raising the crane left the machine swaying in the wind without proper lateral support.

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.

Residents along the Pacific Coast Highway (California Highway 1) are cut off from the outside world after a 2017 storm caused the Pfeiffer Canyon Bridge near Big Sur to buckle. Experts reveal how the construction method of the old concrete bridge left it vulnerable to erosion on the steep coastline.