Perhaps one of the most difficult technical challenges of drawing is creating illusionistic images, mazes, or steps. Like in the movie "Inception," illusionistic spaces involve a dream-like atmosphere and paradoxes in structure, like a neverending staircase. If you're interested in stretching the limits of your mind, go see "Inception." Just kidding. Do go see it, but also check out this drawing tutorial.
You'll learn how to create a large staircase space with balls balanced atop certain steps.