Answer:
I break down buildings, I crumble mountains but you can't see me. What am I?
What can fill a room but takes up no space?
Can not be bought, Can not be sold, Even if it's made of gold. What is it?
I run around the city but I never move.
I have no bed to sleep and no palace to live. I don't have a single coin but I am known as king. What am I?
What is always coming but never arrives?