Some Ambiguous Objects

Here are some ambiguous objects:

		1. The Schroeder staircase: Is this staircase rightside up or upside down (which is the wall closest to us)? You should be able to see the ambiguity without viewing this upside down.
		2. The Necker cube: Which face is in front?
		2a. The Necker cube, part 2: One corner is convex towards you, one is concave. Which is which? This is one of my favorites, as I can't get one of them to stay convex or concave; it changes over and over.
		2b. The Necker cube, part 3: Is this a small cube in a corner, or a cubic bite out of a larger cube?
		3. Slice of pie or missing slice of pie: Is this the last remaining slice of pie (seen upside down) or is it a whole pie with one slice missing?

The objects at Some Impossible Objects are ambiguous in a somewhat different way.