You can use either BSP maps, or create your own 3D room engine. There are many ways to creat a room engine, depending on what version of DB you have, Classic or Pro. If you have classic you can make static objects for walls, desks, etc... With pro it is a little harder, no static objects. It is suggested that you use BSP maps when working with Pro. Very fast, but you can't use ghosted objects. Not yet anyway. Check out tutorials from the DB website.
Good Luck.
Xander - Bolt Software
It doesn't matter if it is confusing, as long as it works