Why Are Manhole Covers Round? (Most Fail This Microsoft Question) | Smartest Year Ever (May 5, 2025)

Why are manhole covers round? In this episode of Smartest Year Ever, Gordy breaks down one of the most deceptively clever questions in interview history. From physics and engineering to human behavior and tech hiring practices, the shape of a manhole turns out to be a masterclass in practical design.

Made famous by Microsoft interviews in the 1990s, this question still pops up today—not because it’s about manholes, but because it reveals how you think.

Can a square fall in? Yes. Can a circle? Never.

Join Gordy as he unpacks the real reasons round manholes make the cut—safety, strength, simplicity—and why this shape has become a symbol of smart design both above and below ground.

Sources:

• Popular Mechanics. (2016). The real reason why manhole covers are round. Hearst Digital Media. https://www.popularmechanics.com/technology/infrastructure/a25300/why-are-manhole-covers-round/
  

• Smithsonian Magazine. (2016). Why are manhole covers round? Smithsonian Institution. https://www.smithsonianmag.com/smart-news/why-are-manhole-covers-round-180961328/
  

• Thompson, C. (2012). The interview question that stuck around. The Atlantic. https://www.theatlantic.com/technology/archive/2012/07/the-interview-question-that-stuck-around/260104/
  

Music thanks to Zapsplat. #Engineering #FunFacts #SmartDesign #InterviewTips #UrbanPlanning #SmartestYearEver #DailyFacts