It is basicly a cylinder with mirrors. As you looks into one end, light entering the other creates a colorful pattern, due to the reflection off of the mirrors In Turkish it is also called as "flower binoculars". It is because of the shapes and fractals those mirrors create when you look through it.
I connected it to my mobile phone camera and here are some results:
|That is the result of looking to my ceiling at home|
|And that is my mother actually :)|
That is what mine looks like. (Yeah it could have looked better with a cooler design :) but the function is satisfactory.) Most people know about these actually but here are some more information you might have skipped.
It is produced by the Scottish inventor Sir David Brewster. The name is derived from Ancient Greek words: Kalos (beautiful, beauty) - Eidos (that which is seen: form, shape) - Skopeō (to look to, to examine) hence meaning "observer of beautiful forms".
In the cylinder usually three mirrors are placed at an angle to one another, (usually 60°) so they form a triangle. This setting creates several duplicate images of the objects.