no, you have to use a skybox. See the tutorials section of this site for help on those.
If you use bsp, simply set the texture to 'caulk' where you want to see through the level. This means you will be able to see the sky outside.
If you use bsp, simply set the texture to 'caulk' where you want to see through the level. This means you will be able to see the sky outside.