I've found Google Sketchup actually invaluable for building up "models" of important places such as buildings, so I can get a better feel for how they look; even a plan drawing just doesn't quite capture the right feel, and ultimately I create these things to make it easier for me to envisage "being" there.
Same here. I used it to design a rotating ring on a starship. My puny human mind couldn't properly conceive a structure where "gravity" essentially pulled outward, and I needed rooms, airlocks etc to plan a chase scene.
From Hex
I write stories in which the characters don't move about very much.
Or the laws of physics don't apply