[post_page_title]Manhole covers[/post_page_title]
You walk over these things day after day, but have you ever considered why manhole covers are perfectly round? In past civilizations, like Ancient Rome, these were actually square shaped slabs of stone.
Unfortunately, the sharp corners and gaps along the edges led to plenty of accidents for unsuspecting pedestrians. However, placing a round manhole cover over a round hole eliminated this problem, while making it virtually impossible for the cover to fall inside the hole.
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