> I always wondered why tools like Doom (other better FPSs are available) aren't used to familiarise people with building layouts.

Because Columbine, that's why. In the 90s, kids used to recreate their college campuses, etc. in Doom. Then Columbine happened, and such things were viewed as possible mass-murder prep.

Doom is primitive by today's standards anyway. I hear tell Unreal Engine is sometimes used for architectural visualizations, etc.

> I'm sure there are Doom levels that I haven't played in years that I could walk round confidently [1] if they suddenly became real.

Given that Doomguy moves at approximately 50 mph, it'd take real-world you quite a bit longer to explore those real-world levels.