ARIADNE: What sort of tricks?
ARTHUR: In a dream, you can cheat architecture into impossible shapes. That lets you create closed loops, like the Penrose Steps. The infinite staircase. See... Paradox. A closed loop like this helps you disguise the boundaries of the dream you've created.
ARIADNE: How big do the levels have to be?
ARTHUR: Anything from the floor of a building, to an entire city. But it has to be complicated enough for us to hide from the projections.
ARIADNE: A maze.
ARTHUR: And the better the maze-
ARIADNE: The longer we have before the projections catch us.
COBB: We need you there to tailor compounds to our particular requirements.
YUSUF: Which are?
COBB: Great depth.
YUSUF: A dream within a dream? Two levels?
YUSUF: Not possible. That many dreams within dreams would be too unstable.
COBB: I've done it before. You just have to add a sedative.
YUSUF: A powerful sedative. How many team members?
SAITO: Six. The only way to know you've done the job is if I go in with you.
COBB: There's no room for tourists on these jobs, Mr. Saito.
SAITO: This time, it would seem there is.