The Worst: Stupid Engineering Mistakes
There's a great article up on wired describing some of the most stupid engineering mistakes that have plague modern human history. Here's my favorite one:
Purity Distilling Company tank, 1919
You gotta keep your molasses somewhere - how about a rickety tank 50 feet tall and 90 feet in diameter in the middle of Boston? The structure was painted brown to hide the leaks. Eventually it burst (possibly exploding from fermentation), sending waves of molasses up to 15 feet high into the city and killing 21.