Answer:
I occur twice in eternity. And I'm always within sight.
Lovely and round, I shine with pale light, Grown in the darkness, a ladyβs delight.
What falls down but is never injured?
If you can get this professional's attention you can get where you need to go for a price.
I can be as thin as a picture frame but my insides have many things you can see.
What is always coming but never arrives?