another major reason, manholes are round bcos the cover wont go in the manhole even if placed in any direction. However a square cover would go in, incase the side is placed diagonally.
Never seen a plant : may be he means he has never seen a factory.
I would choose upper berth since i can sleep or sit anytime without disturbing others.
manholes are circular because of economy,man can go down and come out easily, no chances of injury and also he has not to position himself while going down or coming up which is not possible in square or rectangular shape
