If you live in a big city in a cold climate, you should keep an eye out for 100-pound cast-iron manhole covers suddenly launching 50 feet into the air. It’s unnervingly common and we’ll tell you why. Learn more about advertising on the HowStuffWorks podcasts at www.howstuffworks.com/advertisers.htmAnd to learn about your ad choices when listening to podcasts, visit https://www.howstuffworks.com/privacy.htm#ad-choices
If you live in a big city in a cold climate, you should keep an eye out for 100-pound cast-iron manhole covers suddenly launching 50 feet into the air. It’s unnervingly common and we’ll tell you why.