How do i make a flat circle I need to make a flat circle as a floor for one of my objects, but I don't know how to make a circle.

I have tried different methods, but they don't work. 

I have tried to make a mesh circle but nothing comes there, so can anyone help me?
Add mesh circle, set the faces from ngon to triangles. Also make sure that you are NOT in wireframe. The circle should show in viewport + final render + viewport render. If it does not, please tell me! I would be happy to help further.
Here's a picture of setting this:
Before:  After 

Here are pictures of the circle before and after:


After: