Top 10 Optical Illusions

I think I solved this - Some steps of the staircase are slanted downwards, such that it evens out

Probably my favourite.

This one is definitely my favourite one. Never looks like Tile B and Tile A are the same colour, unless you put your fingers on it.

You view things toward the horizon as larger than when further away from the horizon.
We even see it in real life with the Sun and Moon "rising" and "setting".

You either see a young woman (the wife) or the old woman (the mother in law).

This image is on a whole new level of illusion. You may look it up at your own risk, but be warned: staring at the image for long enough literally changes the way your brain works, so that black and white stripes look weird for anything up to 2 years.

The stairs appear the same no matter if the image is right side up or upside down.

Are you seeing 2 faces staring at each other or a vase?

When you stare at the dot or cross, the surrounding colors seem to fade.

When polygons gain so many sides, they appear circular.
Of course circles have 0 sides and aren't polygons.

Just like the "circular polygons", the polyhedrons start to look spherical when they have enough sides.
Spaceship Earth at Epcot is made up of a bunch of triangles and looks like a ball.