my level :-|

[jens]

You can do a small step down by building it with planes. So you have the main plane for the floor, then you do vertical plane that is 0.25 (or whatever you like) tall, that meets the bottom floor located 0.25 below the main floor.

Doing the outside part from doom would be easy, you can add a skybox to the level, this is in the level settings in the level editor. To begin with you can set a simple color value as a skybox.

To take screens in Amnesia you use F8.