I agree with the stuff Kitten Champion suggested - warp the plane around them, change the map as they walk through it. A corridor that was there earlier might be longer or shorter. A door could appear when they weren't looking. A room could be totally different the second time they visit it.
Also, and this might be hard to pull off but perhaps more in line with your inspiration, have them meet aspects of their own personalities. Force some introspection while messing with their heads.