In this picture, a drawing of M.C. Escher is hidden in a very special way. You must put a cylindrical mirror on the well, in the reflection you can see the face of Escher.
Just to inform you : people have always been perverts. But back in the days, they had to cover it up a little. When you look at this picture from 1538, you notice a man and a woman to the left, and a somewhat strange landscape to the right. When you held the original and looked at it from the right, in a very sharp angle, you saw the couple doing a little more than kissing.
Actually this is a deformation. The landscape served as cover for the book "The Mysterious Island" from Jules Verne. If you place a cylindrical mirror at the top of the landscape, you can see the face of Verne himself.
Want to loose weight fast ? It doesn't get any faster than on this billboard. Look at it from the front and you'll see a rather fat lady. Then walk to the side of the board and you'll see the same woman, but a lot thinner. And of course she's presenting the weight-loss product there that made it all possible.
This very original coaster was made for Guinness to revive their tagline. When the coaster is placed, the text on it is unreadable. When the glass is placed on it - still nothing. But when the beer is poured in the glass, you can read the text perfectly in the reflection on the glass (those who wait ...). To really understand the tagline, look for it on Youtube.