Manhole covers don't have to be merely heavy plain disks to metal; they can be ornate and decorative. Some older varieties before the era of modern lighting have glass jewels inset to provide light from above to below.
And did you know that there may possibly even be a manhole cover orbiting Earth at this very moment? An 'experiment' during the early days of nuclear weapons testing may have blasted a 700-lbs. manhole cover into Earth orbit!

"...cast-iron manhole covers come in many assorted designs and patterns meant solely to decorate the street above. While collecting manhole covers as a hobby is impractical due to their weight and size, people can and do as a hobby collect images of them from around the world."

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