Vitruvius' De Architectura
The most authoritative source of information on Roman architecture is the ten book treatise, De Architectura by Marcus Vitruvius Pollio. Using both extant treatises on architecture and his own experience as an architect and builder, Vitruvius wrote a detailed study of existing buildings and made recommendations about how to build new ones. The fifth book deals with the theater. In the fourth chapter he discusses such subjects as site selection, foundations, and acoustics. The sixth chapter is concerned with the auditorium and the stage building. He even includes sections on scenery and scene shifting by means of triangular prisms (periaktoi), etc. The publication of De Architectura in 1486 greatly influenced Renaissance theorists and architects, especially Andrea Palladio in constructing the Teatro Olympico in Vicenza which still stands.

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1. The plan of the theater itself is to be constructed as follows. Having fixed upon the principal center, draw a line of circumference equivalent to what is to be the perimeter at the bottom, and in it inscribe four equilateral triangles, at equal distances apart and touching the boundary line of the circle, as the astrologers do in a figure of the twelve signs of the zodiac, when they are making computations from the musical harmony of the stars. Taking that one of these triangles whose side is nearest to the scaena, let the front of the scaena be determined by the line where that side cuts off a segment of the circle (A-B) , and draw through the center, a parallel line ( C- D ) set off from that position, to separate the platforrn of the stage from the space of the orchestra.

2. The platform has to be made deeper than that of the Greeks, because all our artists perform on the stage, while the orchestra contains the places reserved for the seats of senators. The height of this platforrn must be not more than five feet, in order that those who sit in the orchestra may be able to see the performances of all the actors. The sections (cunei) for spectators in the theater should be so divided, that the angles of the triangles which run about the circumference of the circle maY give the direction for the flights of steps between the sections, as far as up to the first curved cross-aisle. Above this, the upper sections are to be laid out, midway between (the lower sections) , with alternating passage-ways.

3. The angles at the bottom, which give the directions for the flights of steps, will be seven in number (C, E, F G H, I, D). the other five angles will determine the arrangement of the scene: thus, the angle in the middle ought to have the "royal door" (K) opposite to it; the angles to the right and left (L, M) will designate the position of the doors for guest chambers; and the two outermost angles (A, B) will point to the passages in the wings. The steps for the spectators' places, where the seats are arranged, should be not less than a foot and a palm in height, nor more than a foot and six fingers; their depth should be fixed at not more than two and a half feet, nor less than two feet.

4. The roof of the colonnade to be built at the top of the rows of seats, should lie level with the top of the scaena, for the reason that the voice will then rise with equal power until it reaches the highest rows of seats and the roof. If the roof is not so high, in proportion as it is lower, it will check the voice at the point which the sound first reaches.

5. Take one sixth of the diameter of the orchestra between the lowest steps, and let the lower seats at the ends on both sides be cut away to a height of that dimension so as to leave entrances (o, P). At the point where this cutting away occurs, fix the soffits of the passages. Thus their vaulting will be sufficiently high.

6. The length of the scaena ought to be double the diameter of the orchestra. The height of the podium, starting from the level of the stage, is, including the corona and cymatium, one twelfth of the diameter of the orchestra. Above the podium, the columns, including their capitals and bases, should have a height of one quarter of the same diameter, and the architraves and ornaments of the columns should be one fifth of their height.
The parapet above, including its cyma and corona, is one half the height of the parapet below. Let the columns above this parapet be one fourth less in height than the columns below, and the architraves and omaments of these columns one fifth of their height. If the scaena is to have three stories, let the uppermost parapet be half the height of the intermediate one, the columns at the top one fourth less high than the intermediate, and the architraves and coronae of these columns one fifth of their height as before.

7. It is not possible, however, that in all theaters these rules of symmetry should answer all conditions and purposes, but the architect ought to consider to what extent he must follow the principle of symmetry, and to what extent it may be modified to suit the nature of the site or the size of the work. There are, of course, some things which, for utility's sake, must be made of the same size in a small theater, and a large one: such as the steps, curved cross-aisles, their parapets, the passages, stairways, stages, tribunals, and any other things which occur that make it necessary to give up symmetry so as not to interfere with utility. Again, if in the course of the work any of the material fall short, such as marble, timber, or anything else that is provided, it will not be amiss to make a slight reduction or addition, provided that it is done without going too far, but with intelligence. This will be possible, if the architect is a man of practical experience and, besides, not destitute of cleverness and skill.

8. The scaena itself displays the following scheme. In the center are double doors decorated like those of a royal palace. At the right and left are the doors of the guest chambers. Beyond are spaces provided for decoration - places that the Greeks call periaktoi, because in these places are triangular pieces of machinery, which revolve, each having three decorated faces. When the play is to be changed, or when gods enter to the accompaniment of sudden claps of thunder, these may be revolved and present a face differently decorated. Beyond these places are the projecting wings which afford entrances to the stage, one from the forum, the other from abroad.

9. There are three kinds of scenes, one called the tragic, second, the comic, third, the satyric. Their decorations are different and unlike each other in scheme. Tragic scenes are delineated with columns, pediments, statues, and other objects suited to kings; comic scenes exhibit private dwellings, with balconies and views representing rows of windows, after the manner of ordinary dwellings; satyric scenes are decorated with trees, caverns, mountains, and other rustic objects delineated in landscape style.