Mystery riddles with simple answers

I look flat, but I am deep, Hidden realms I shelter. Lives I take, but food I offer. At times I am beautiful. I can be calm, angry and turbulent. I have no heart, but offer pleasure as well as death. No man can own me, yet I encompass what all men must have.

I visit you every night even if you don't call me. I'm lost every day. What Am I?

This is as light as a feather, yet no man can hold it for long. What am I?

I have cities, but no houses. I have mountains, but no trees. I have water, but no fish. What am I?

If I have it, I don't share it. If I share it, I don't have it. What is it?

One winter day, there was a man standing in the middle of someone's front yard. The person stayed there for several weeks without moving and the owner of the yard didn't mind. Eventually the man left. Who was the man?

What comes down but never goes up?

What goes through a door but never goes in and never comes out?

You can hold it without seeing or touching it! What is that?

All about, but cannot be seen. Can be captured, but cannot be held. No throat, but can be heard. What is it?