The picture of the right shows windows situated above walkways, making it look 3D. You can even create the illusion of a construction behind and above the floor level beyond the window, like in Addictiv Map01 (574 Kb). This trick is done by suspending a middle texture into the air to create illusion of a wall between the windows and the walkway below while also lowering a SKY ceiling to create the window's view.

SECTORS 1 : ceiling/floor 320/0; 2 : ceiling/floor 320/0; 3 : ceiling/floor 256/0, ceiling has sky texture; 4 : ceiling/height 128/0 LINEDEFS a: has front/back middle texture (Y=128, Y offsett=128, lower pegged); b : same properties as 'a', missing front upper texture; c : nothing special, leave as is.

All nodesbuilders I've used so far are capable of this trick. Basically, the wall between the open sector and the window is a 2-sided texture suspended into the air.You might want to lower the ceiling of sector 3 to prevent floating monsters from wandering through the 'fake' middle texture. A nice effect can be achieved by leaving a distance between the upper level of the 2-sided 'b' texture and the ceiling of sector 3, achieving the effect seen in Addictiv Map01.