Perspective (from Latin perspicere, to see through) is an approximate visual representation capturing the depth of an image on a flat surface as it is seen by the eye. The objects in the scene are drawn smaller as their distance from the observer increases and the details are foreshortened, where the size of an object's dimensions along the line of sight are relatively shorter than dimensions across the line of sight.
For perspective to work - for a 3D image to fool the eye into seeing depth and for the relationship of objects to appear believable and in proportion, it requires that the veiwer look at it from a specific angle and position.
The image of the dry stone Venusgate we built in 2011 appears to pop up off the page in the first drawing.
In the drawing below , looking at things from above, you can see how stretched that concept is.
This photo of the Venusgate is still only just an illusion.
The image will distort or break up or disappear altogether when viewed from an 'incorrect' position.
It's only the stones in the real life structure that 'make' the real Venusgate, and put everything else in perspective.