Tantalizing Trivia: Manhole Covers

Why are manhole covers round?

My brother mentioned he was once asked this question in a job interview, and the interviewer said my brother was the only person who ever knew the answer.

Come to find out, there are many answers:

A round manhole cover can’t fall through its circular opening
Round doesn’t need to be rotated until it fits the opening
Round can be rolled, so it’s easier to move
Round tubes are the strongest shape against the compression of the earth, so the cover needs to be round, too.

So if you’re ever asked this question in a job interview, rock it!