how to control the scene size?

I have set up a test scene where the camera can be moved with the arrow keys, left and right keys rotate on the y axis and up down moves forward or backward on the z axis, makes like driving. Have a ground and sky set up as plains. Problem I got is after I move so far the sky and ground disappear and all I can see is white, like I ran off the scene. Is it possible to make the scene or map area bigger so I can go farther without running off the scene or map.

thanks in advance,

mike.