Explain this:

[Greg Baehman]

Give it your best shot . . .

[Mike Koneski]

The Penrose Tribar Illusion is a classic.

[James L. Martin]

From another angle

[Dean Romig]

M C Escheresque....





.

[edgarspencer]

I'm so beat when I head up for the night, if I didn't know better I would tell you Escher designed my stairs.