Any of you all ever notice these while walking down city streets? Some are rather boring, but others can be rather interestingly styled. Some cities even go as far as decorating them for a particular neighborhood! Manhole covers can be sort of like coins, although obviously much larger and heavier
In Washington DC, they were having problems with the deteriorated electrical wiring in the manholes sparking, and igniting sewer gas. It is all too frequent occurance there to have explosions underground that send manhole covers flying!