Impossible Traingle as a set of cubes in parallel projection | created by Oscar Reutersvard
At first glance the triangle seems like a simple geometrical shape .. But, as you concentrate you'll find it is really impossible to build in real life.
In 1934, at the age of 18, while he was a school student, Swedish artist Oscar Reutersvard drew the first ever Impossible triangle composed of a series of cubes in perspective.
Later in 1980 this impossible figure uses in Swedish postage stamps as-well.