Instruction on the Fortification of Cities

From this figure it is found how,
from the front base plan, the
upper part with all its contents
is seen to be tapered toward the sides.

A geometric diagram illustrates the principles of linear perspective. A central vertical axis connects point ‘h’ to point ‘f’ and terminates at a vanishing point ‘A’ at the apex of a large triangle. A horizontal baseline ‘d-h-e’ serves as the anchor for construction. Below it, a trapezoidal plane represents a receding architectural or floor plan, with diagonal lines converging toward point ‘A’. Points and lines are labeled with letters ‘d’, ‘e’, ‘h’, ‘f’, ‘A’, and ‘m’. Decorative flourishes are visible on the left side of the diagram.

In the same way that one has tapered verüngetthe architectural process of narrowing a wall or structure as it rises to increase stability and provide a defensive slope these walls, and the fields the spaces or bays between structural elements between them, toward the sides in the upper plan, one must also do so according to the length of the ground plan. Therefore, draw the line d-h-e as long as the front base is, and mark upon it all the thicknesses of the crosswise buttress-walls original: "strebmauren" and the widths of the fields between them in the rear rectangular section of the plan. Then, draw a cross-line through the middle of line d-e through point h at right angles, and set point f at its place above.

After that, take the line d-h-e from the upper plan and place it with point h on the previously drawn line h-f, so that it sits near the front dotted line, parallel or equidistant to it. Then draw two straight lines d-d and e-e and extend them out to line h-f, where one places a point A. Then draw straight lines from all points of the front line d-e toward point A until they reach the upper line d-e.

Since this shorter line is now proportionally divided by all the points of the front one, one should then transfer these divisions into the upper plan and, in the rear oblong rectangle fierunga squared or rectangular geometric layout, mark the thicknesses of the cross-walls and the widths of the spaces between them.

But the buttress-walls between the round walls should be divided equally again; the high ones also slightly narrowed at the top into the buttress. One should make the buttress-walls on the innermost part of the outer arc as thick as the buttresses have become in the tapering. If one draws their sides toward point f, they will diminish correctly. The thin buttresses in between should be made as thick as the rear thin buttresses have become. And note that what I call the "rear" of this building faces toward the city. All of this I have drafted below, as will be seen in the two following figures.