Optical Illusion: Stairs of Watchtower
This picture shows the inner side of the watch tower on the mountain Great Kornberg, part of the chain of mountains Fichtelgebirge in Bavaria. It's no photomontage. The only manipulation I did was removing the handrails.

At a quick view one could think, the left staircase leads upstairs, but then the way is blocked. Assuming the photographer stood upside and took the photo downwards, the left stairs would also go downwards, this wood be a more meaningful result.

As soon as the webpage has loaded fully, you can cross with your mouse over the picture and by appearing the handrails you can see that this was thoroughly wrong, too.
Foto: Erwin Purucker