You may know Ledoux's famous image of the eye with the interior of his Besançon theater. One could think of Schinkel's equally famous perspective of his Berlin museum in a similar vein, with its extraordinarily compressed layers of columns and stairs as an experiential lens between the building and the city.
By the time the figures in the drawing reached the upper terrace and can look across the Lustgarten back to the city, they have crossed the most elaborate sequence of thresholds. First there was the row of columns. The museum is a three-story building--you can see it on the fenestration of the lateral walls--but on the front it appears as a much taller single story volume sitting on a base. The dimensions of the colonnade work at the scale of the Lustgarten, the open space in front the building. To reach the top of the base, the figures in Schinkel's perspective had to climb the wide expanse of steps in front of the columns. Here they had to find the center, as only four of the columns reach the back wall of the loggia. Afterwards they went through a large frame and turned 90 degrees to face a flight of stairs parallel to the facade. At this point they had completely lost any connection with views of either the inside or the outside. When they reached the landing--pay attention to this--they turned out--yes, the next flight of stairs is not a layer in but a layer out!--and climbed back to the center, where they re-emerged to the city but at a much higher level.
Think about it this way: when the figures crossed the first threshold of the building, the encountered the bases of the columns. Now, having reached the upper outdoor terrace, they can almost touch the monumental Ionic capitals, as the fluted shafts of the columns in the foreground frame their views.
It is as if the building had blinked, closing its eye and opening it again to a new and surprising experience of the city.