Answer:
I am heavy forward but backward I'm not.
I have no weight but I could destroy a mansion. What am I?
I am the place to turn when nature calls.
So cold damp and dark I am. To stay you would refrain yet those who occupy me do never complain.
I lose my head in the morning and regain back it at night.
As round as an apple. As deep as a cup. All the king's horses can't pull it up.