THE AMES ROOM
Your brain is fooled into believing that the room is rectangular, when actually it is more of a trapezoid shaped room.  The girl on the left is simply farther away than the girl on the right.
This is a version of the Ames Room built somewhere in France.
Believe it or not, the tops of these two tables are of identical size and shape ( they are perfectly symetrical)

Don't believe it?  Click Here

THE HERMANN GRID -

COUNT THE BLACK DOTS NOT THE WHITE ONES.
CAN YOU SEE A TRIANGLE?
Actually, there is no triangle, just 3 Pac Man shapes.

STARE AT THE BLUE DOT IN THE CENTER WITHOUT MOVING YOUR EYES AND WATCH IT ALMOST COMPLETELY DISAPPEAR
CHECK OUT THE MOON ILLUSION
BACK TO THE ILLUSIONS PAGE.
THE HARLEQUIN CUBE - by Karen Combs
IS A CUBE SHAPED PIECE MISSING OR IS A SMALL CUBE FLOATING IN FRONT OF THE LARGER ONE?
CAN YOU FIND 3 HIDDEN FACES?
3 IN ONE CUBE
FIND THE 9 HIDDEN PEOPLE IN THIS ONE
IS A PIECE OF CHEESE MISSING OR NOT?
IS THE MAN IN THE BACKGROUND LARGER THAN THE SMALL MAN IN THE FOREGROUNG?

MEASURE  & SEE FOR YOURSELF
ARE THOSE HORIZONTAL LINES CROOKED OR PARALLEL?
Do you see these as bumps bulging out, or indentations?

How about this one? 
They're the same picture, but one is turned upside down!
ILLUSIONS OF APPARENT MOTION
The Frazier Spiral -Do you see the black and white spiral?

Look again!

There isn't any spiral, just a series of concentric circles.