The Chateau - Page 2
Here is another picture of the same building, but now the camera has been held level, and we can also see a little more of the tree!
We feel comfortable with level horizons, so in the first photograph, the steeply sloping hill in the foreground has been made to appear level by tilting the camera, and carefully including only a portion of the tree but not the trunk. Since we are very comfortable with the level horizon, our mind tells us that the building must be leaning, especially since there are no other clues in the picture to tell us otherwise.
However this picture makes everything clear. There is a steep hill in the foregound, and the building is not actually leaning at all. Now that we can also see the tree trunk, there is an extra clue to confirm our new glimpse of reality!