The opportunity did not arise until 1934, in connection with systematizing and beautifying with lawns the borders of Mussolini’s grandiose new Via dell’ Impero, already mentioned as having been cut through slums from the Coliseum to the Piazza Venezia. The two projecting columns of the Forum Transitorium (“Forum of Nerva”), southeast of the Forum of Augustus, were cleared, under the direction of A. M. Colini, of medieval and modern detritus down to their plinths (Figs. [9.2] and [9.3]); the podium of the Temple of Minerva, at the end of this Forum, uncovered; and the peperino wall behind the projecting columns isolated. Close in back of this wall, on the Forum of Peace side, Colini found large columns in African marble, which, he inferred, marked the missing northwest side of that Forum. Its general location had been known since 1818, but only now was there a precise point in modern Rome’s subsoil from which, with the help of the Marble Plan, the true dimensions of Vespasian’s portico could be measured. Also, another fragment of the Marble Plan, not joining the two previously mentioned, showed the very stretch of wall and the columns which Colini had been excavating, as well as the plan of Minerva’s temple, whose podium he had uncovered.
Now that the plan of Vespasian’s Forum could be precisely fitted into the plan of modern Rome, it became clear that some fragments of large fluted white marble columns, found in the southeastern part of this area as long ago as 1875, belonged to the part of the portico where the larger columns shown on the Marble Plan would fall. Colini now made another join on the Marble Plan, adding to Lanciani’s fragment another piece, previously known but not connected, which showed the Temple of Peace at the back of the portico. It was an apsidal building, wider than it was deep, with a pedestal for the cult statue indicated in the apse. If it survived today it would come within a few feet of touching the north corner of the Basilica of Maxentius. The south side of the rectangular hall to the right of it coincides with the actual wall of the church of Sts. Cosmas and Damian, which was the findspot—in 1562—of the fragments of the Marble Plan itself. This square hall was one of the libraries of Vespasian’s Forum. Since the principle of axial symmetry nearly always operates, justifying the hypothesis that what appears on one side of the axis of a Roman plan will have a twin on the other; and since the Romans usually built their libraries in pairs (one Latin, one Greek), Colini quite reasonably restored on paper another rectangular hall to the left of the apsidal temple. A section of the polychrome marble pavement, excavated by Colini east of the church wall, was less than an inch thick, too thin to be exposed to the weather. Colini inferred that it must have been part of the flooring of the library in which the Marble Plan was displayed.
An ingenious combination—“joins” recognized on the Marble Plan, actual excavation, and inference—had now made the Forum’s general outline clear, but Colini was not yet done. Overlying the Forum’s outer (northeast) perimeter wall, as he had plotted it, rose the medieval Torre dei Conti, built by the brother of Pope Innocent III. Re-examining beneath this tower the ancient remains, in squared travertine, ordinary tufa, and peperino, Colini was able to establish that they formed part of Vespasian’s Forum, a great ornamental rectangular niche on its northeast side, with two columns of African marble in front of it. Symmetry would dictate another matching niche further to the southeast in the same wall, and a pair on the opposite side to correspond. Pink granite columns found in the excavations belonged to the portico; marble gutters proved that it had a pitched roof. Finally, in 1938, the plan was complete enough for a model of the Forum to be made ([Fig. 9.4]) for Mussolini’s Mostra Augustea della Romanità, a great exhibition of models and photographs of Roman architecture and engineering, casts of inscriptions, and replicas of artifacts.
* * * * *
But Vespasian’s Forum, famous as it was, and valuable as its restored plan is to illustrate archaeological inference at work, is overshadowed by his mightiest monument, which has survived to become the very symbol of pagan Rome to modern times: the Flavian Amphitheater or Coliseum. More perhaps than any other classical monument, its stones are steeped in blood and memories; in the blood of gladiators and wild beasts, and perhaps of Christian martyrs, in memories of medieval battles, Renaissance plundering of stone (much of the travertine in St. Peter’s came from it), and Victorian moonlight visits. Having resisted earthquakes, fire, and demolition, it is now menaced by the vibrations of modern traffic. Work on strengthening its walls against this new threat has been going on since 1956.
For sheer mass the Coliseum deserves its name. It is a third of a mile around, and the Italian engineer G. Cozzo has calculated that 45,000 cubic meters of travertine went into its outside wall, over twice as much into the whole structure. But the achievement here is not mere massiveness, but precise engineering, careful calculations of stresses and strains, avoidance of crowding at entrances and exits, perfect visibility, ingenuity in the arrangements for getting the wild beasts into the arena. (Perhaps this is the place to recall that it was upon the Coliseum that Charles Follen McKim based his design for the Harvard Stadium.) The site chosen, the bed of the pool of Nero’s Golden House, was good propaganda and good engineering. Propaganda-wise, it made for good public relations to turn a detested Emperor’s pleasure grounds into a place for public enjoyment. (Neither Vespasian nor the Roman mob would have thought of the slaughter of men and beasts as anything but enjoyable; their attitude at best was that of Hemingway to a bullfight.) From the engineering point of view, it saved much costly excavation to pump out the pool and use it for the substructure of the arena, and in the low, soft ground, footings could go deep: eight feet of concrete under the cavea. Besides, the huge mass of debris from the demolished Golden House could be cannily reused in the new fabric. The first step was to erect a skeleton of travertine piers, a double row, built of squared blocks held together not with mortar but with metal clamps. The holes where these clamps were wrenched out, 300 metric tons of them, in the metal-starved Middle Ages, are visible today throughout the fabric. Differences in construction suggest that the huge project was divided into four quadrants, each assigned to a different contractor. Most of the work is honest, so that, for example, one cannot get the proverbial penknife blade into the joints between the blocks of the piers, but in the northwest quadrant the work is shoddy. This is precisely the section that has given the most trouble under the strain of the traffic vibrations of modern times.
Inside the second concentric ellipse of piers begins a set of radial walls which supported the seats. The slope of the seats was perfectly calculated for perfect visibility. The vaults of the lower levels were left open until the upper level piers were finished. This made possible the use of derricks to lift heavy blocks to the upper levels. The third-story piers have one course of blocks projecting, to provide a step to support the scaffolding required for building the wall on the fourth level. This wall is built of smaller blocks than those used on the lower levels, to facilitate lifting, and it is full of second-hand materials; column drums, for example, which may have come from the Golden House. The outer face of the fourth-level wall is equipped with 240 consoles, projecting brackets jutting out from the wall to support masts. Corresponding to each in the cornice above is a hole for the mast. The mast, Cozzo argues persuasively, was fitted with rope and pulley. The rope descended obliquely and was fastened to another below which ran elliptically at a convenient height above the podium of the arena. Awnings, fixed to these ropes, could be rolled up or down in strips as the sun’s position dictated. Awnings being made of canvas, this duty was assigned to detachments of sailors—the logical Roman administrative mind at work.
When the skeleton was finished, the space between the piers in the radial walls was filled in, on the ground level with tufa, on the second level with lighter materials, brick and cement. Only then were the vaults completed. The stairs were ingeniously planned to give access from the ground direct to each level separately. This both emphasized distinctions (VIPs in the lowest tier, women at the top; compare the separate second-balcony stairs in modern theaters) and facilitated entrance and exit. Each outside entrance—there were originally eighty—bears a Roman numeral. This corresponded to a number on the admission ticket, and divided the 45,000 or 50,000 spectators into manageable groups.
The arena proper was surrounded by a wall, high enough to protect the spectators from the beasts (VIPs not being regarded as expendable), but not so high as to block the view of the arena from the seats behind. Slots in the top of this wall are the postholes for a dismountable fence which supplied additional protection. Literary sources say it was of gilt metal surmounted by elephants’ tusks. In front of the fence ran a catwalk where archers were stationed to shoot beasts which got out of hand.
The arena was originally floored with wooden planking, removable for the mock naval battles which were staged here in the early years of the amphitheater’s existence. Since this had been the site of Nero’s artificial pool, flooding must have been comparatively easy. But though slaves fought and killed each other in these naval battles, they were less sanguinary, and therefore less popular, than gladiatorial contests or beast fights, and changing back and forth from murder on water to murder on land was a nuisance, so the naval battles were transferred elsewhere. The area below the arena floor was then filled in with complicated substructures, which finally revealed their secret to Cozzo in 1928.