Help with custom Lighting

Ok so anyways adding light to an area is a piece of cake. what i need to know is how do i make it so an area is pitch black? I want to have an indoors scene inside a cathedral and i want it to be dark, the only light thats coming through i want to be from the lanterns and stuff that im gonna put around it.

Here is my idea:

Make the entire map pitch black then use custom lighting where you need lighting.
For outdoors areas increase the # of lighting objects you have.
Use custom lighting models that make it seem like like is entering through a window.

this will make everything completely black;
to return to default, use eg for Ashenvale lighting;

ty
id +rep you, but it doesnt seem to let me for some reason.