Manholes are an essential yet overlooked part of urban infrastructure. They provide access to the underground systems that are important for maintaining the flow of water, sewage, and electrical ...

When walking down the street, you probably don’t stop to notice the manholes on the road. And if you have, you may not have realized that nearly all of them are round—or that those with other shapes ...

Manhole covers are usually round. Most people probably don't spend their days thinking about why that is. But there's actually a cool geometry reason behind the design: Circle-shaped things can't fall ...