3d Skybox

[Haggis]

I have only built 1 map which i have uploaded to this site most of it is inside except for 1 area which is sealed with the skybox texture.I am going to attempt a 3d skybox but i am a bit confused about something.I have read the tutorials and grasp the fact that you pick objects in your map which are on the outskirts of your map,even useing the ground as reference then once you have made some displacements like cliffs and added models you then delete what you used from your full scale map.What has thrown me is badwater and goldrush,in these sky boxes they have made the ground look like it is covering the whole of the original map,here is a pic,

My thinking would be that there would be a big hole in the middle where the original map would be,please help me understand this,cheers.

 

[YM]

They cover the entire area of the map, but they've made sure they're 100% underneath the real world stuff so that there are no nastly lighting problems.
You can cut a hole in the middle if you so wish but either method works just fine.

 

[Haggis]

They cover the entire area of the map, but they've made sure they're 100% underneath the real world stuff so that there are no nastly lighting problems.

Cheers,i thought thats what they were doing but i thought it best to find out for sure.