On the Art of Building

...they command that angles be placed toward the direction from which the force and violence of water or wind, or the weight from a cliff, threatens or attacks, so that it may split and dissipate the injury approaching it, with the front of the walls struggling against the distress, if I may speak so, with solid strength rather than with the weakness of the sides. But if the other lineaments of the building prevent you from being able to use an angle in that place as you intended, a curvature must be used, since a curved line is a part of a circle, and the circle itself, in the opinion of philosophers, is entirely an angle. Furthermore, an area will be placed either on level ground, or on a slope, or on the very top of a mountain. If it is placed on level ground, it is necessary to heap it up and build a foundation, as it were, like a podium; for this, while it contributes much to dignity, also, if it is done, will bring the greatest [protection from] inconveniences. For the inundations of rivers and rains are accustomed to bring mud to level places, by which it happens that the very ground gradually swells; then, too, by the negligence of men, rubble and refuse, which are discarded daily, easily accumulate on level ground. Frontinus, the architect, used to say that Rome in his age had grown on its hills because of the frequency of fires. But in this age, we see that same city entirely buried in ruins and filth. I have seen an old chapel in Umbria placed on level ground, yet it was to a great extent submerged, because of the accumulation of earth upon itself, since that plain extends below mountains. But why should I mention those things which are below the mountains near Ravenna? Below the city walls is that noble temple, for which the entire stone vessel stands as a roof; although it sits by the sea and far from the mountains, it is nevertheless more than a fourth of its height immersed within the ground by the force of time. How deep the raising of any given area should be will be told in its own place, when we speak of these matters not summarily as here, but more distinctly. But it is fitting that every area be made most firm either by nature or by art, regarding which matter I think those should be heard above all who advise that we should examine, by digging a trench or two at intervals, whether the soil itself, by its density or rarity or softness, is capable of bearing the weights of the structure by itself. For if it is placed on a slope, one must take care that the higher parts do not press down with the annoyances of pressure, or that the lower parts, if they happen to move, do not pull the rest into ruin. Indeed, the most firm and, from every part, the most fortified...