Is this cat going up or down the stairs?
Is it a frog or a horse?
This is actually a sheet of paper...
…folded the right way
Three beautiful women?
Now look at this image upside down.
Is this window to the right or left of this wall?
Are shades of red and green the same?
The squares on the left appear darker than those on the right. But they are actually the same color.
Ames Room
Upon entering this room, people of average height seem to turn into dwarfs or giants.