Thanks to the large focal distance of the lenses the result is a magnificent optical effect which means that even objects which are far away seem to be near.
To focus the different distances the screen moves up and down, which allows the screen to focus, just like in a camera. The images in the Camera Obscura can be moved forwards and backwards to visualize the different parts of the landscape. Above one can see the horizon at a certain distance, and below, examine details.
The principal lenses of the optical instrument have a plane astronomic object which is produced with a degree/level/grade from 4” (10,16 cm) to 12” (30,48 cm) of diameter and with focal radiuses which are designed for each building in particular.