Answer:
In Paris but not in France, the thinnest of its siblings.
It holds most knowledge that has ever been said. But is not the brain, is not the head. To feathers and their masters, it's both bane and boonΒ One empty, and one full.
I turn around once. What is out will not get in. I turn around again. What is in will not get out.
What goes in the water red, and comes out black?
I weaken all men for hours each day. I show you strange visions while you are away. I take you by night, by day take you back. None suffer to have me, but do from my lack.
In birth I spring forth, in life I unfold. In death I wilt and die, but rebirth restores all.