What Am I Riddles

Question: Thousands of orphans who lost their old home,
found by others who have lost their own.
To hide a secret that is obvious to all,
becomes even more obvious when the host falls.

What am I?

Question: I stand in one place yet I fill a whole room.
I can be filled with molten rock and come in every hue.

What am I?

Question: In a marble hall as white as milk, Lined with skin as soft as silk, Within a fountain crystal clear, A golden orb does appear, There are no doors to this stronghold, Yet thieves break in and steal the gold. What am I?

Question: What has 6 wheels and flies?

Question: Occurring once in a hundred years and once in thousands. But never in a day or a year or a century.