The Roman Colosseum an Engineering Masterpiece

Engineering the Roman Colosseum While the Colosseum stands, Rome shall stand; when the Colosseum falls, Rome shall fall; when Rome falls, the world shall fall. -- The Venerable Bede quoting an Ancient Anglo-Saxon Peasant Prophecy Perhaps the most enduring symbol of the greatness of the Roman Empire can be seen today in the ruins of the Colosseum. This massive amphitheatre is situated in the middle of modern Rome near the Roman Forum and has become an iconic representation of the Roman Empire at its zenith.

Although estimates vary, analysts believe that at least 50,000 and perhaps as many as 80,000 spectators were accommodated in its capacious dimensions and the Colosseum has become the benchmark by which all subsequent stadia have been judged.

Flush with the treasures and riches of Jerusalem, the builders of the Colosseum spared no expense in its design and construction, but despite its impressive seating capacity and functional design, opinions concerning the aesthetics of the Colosseum have varied over the centuries, with some scholars describing the structure in strictly superlative terms while others have argued that it lacks the aesthetic qualities that characterize other Roman architecture.

To determine the facts, this paper reviews the relevant literature to provide the dimensions of the Colosseum, important architectural details and varying views concerning the end result. Finally, a summary of the research and important findings concerning the engineering of the Colosseum are provided in the conclusion.

Review and Analysis Overview of the Colosseum The location selected for the construction of the Colosseum was a level region situated between the Esquiline Caelian, and Palatine Hills.[footnoteRef:2] According to one historian, "Constructed in the city center, the Colosseum differed vastly from other amphitheatres that were typically located on the outer edge of a city.

It emblematically stood, and still stands, at the core of Rome."[footnoteRef:3] Irrespective of any aesthetic considerations, the dimensions of the Colosseum are truly impressive even by modern standards and its general dimensions are provided at Appendix A.

IN sum, the dimensions of the Colosseum were 189 meters (615 feet) long and 156 meters (510 feet) wide; the structure's base area covers six acres and the height of the outer wall is 48 meters (157 feet), making it as tall as a modern 12-15 story structure.[footnoteRef:4] [2: Gulomar Barbi, "The Colosseum," The World and I, 22(9) (2007, September), 37.] [3: Barbi, "The Colosseum," 37.] [4: Barbi, "The Colosseum," 37.] Although significantly smaller today due to the harvesting of stones for local construction projects, the Colosseum's perimeter was originally 545 meters (1,788 feet) and the central arena's oval was 287 feet long by 180 feet wide, and this enclosure was surrounded by a 15-foot high wall.[footnoteRef:5] A number of different types of locally sourced building materials were used to construct the Colosseum, including a type of limestone ("travetino") stones, tuff (which was used for radial walls and some pillars), ceramic tiles (also used on the walls and for the flooring of the upper levels), and concrete which was used for the vaults.[footnoteRef:6] Although the historical record is unclear on the issue, it would appear reasonable to suggest that the floor of the main arena of the Colosseum was also made from some type of water-proof concrete.

For instance, Grayson notes that, "The Romans restaged battles in the Colosseum so that the vulgar could celebrate famous victories in which the players were actually killed and, if it was a naval engagement, the arena was filled with water."[footnoteRef:7] [5: Barbi, "The Colosseum," 37.] [6: "Colosseum building materials," The Colosseum [online] available: http://www.the-colosseum.net/architecture / materials_en.htm, 3.] [7: Richard Grayson, "History Will Repeat Itself: Strategies of Re-Enactment in Contemporary (Media) Art and Performance," Art Monthly 313 (February 2008), 27] In fact, there were two different types of mortar used in the construction of the Colosseum, with one type (pozzolanic mortar) being waterproof which could account for the ability of Roman engineers to flood the arena for naval battles without flooding the structure's lower levels.

This type of mortar consisted of "pozzolana," made from volcanic ashes that had been sufficiently heated to produce its Portland concrete-type water-proof qualities.[footnoteRef:8] In his study, "The Riddle of Ancient Roman Concrete," Moore reports that Roman engineers discovered by trial-and-error that when a small amount of volcanic ash was reduced to a fine powder and mixed with moist lime, it produced a water-proof concrete that would even cure underwater.[footnoteRef:9] An important finding by Moore was that the Roman engineers also used special construction methods with this type of concrete.

In this regard, Moore advises that, "We have learned that ancient concrete was a simple mixture of wet lime and pozzolan in specific ratios to match the desires of the Roman architect.

We have also learned that the Romans followed a placement method of tamping their stiff mortar into the voids of a rock layer."[footnoteRef:10] By tamping the mortar, the Romans were able to eliminate excess water, thereby increasing the strength of the resulting mixture, a process that was only recently discovered by modern engineers.[footnoteRef:11] [8: "Colosseum building materials," 4.] [9: David Moore, "The Riddle of Ancient Roman Concrete," Roman Concrete (2016).

[online] available: http://www.romanconcrete.com/docs/spillway/spillway.htm, 2.] [10: David Moore, "The Riddle of Ancient Roman Concrete," 4.] [11: David Moore, "The Riddle of Ancient Roman Concrete," 4.] The various building materials used in the construction of the upper levels of Colosseum were undoubtedly moved into place using a human-powered treadmill crane of the type depicted in Figure 1 below. In this regard, one historian reports that, "Columns and other massive blocks were raised by means of a crane with its system of pulleys.

Motive power was supplied by men in a treadmill -- a huge wooden wheel."[footnoteRef:12] [12: Frank Gardner Moore, The Roman's World (New York: Biblo and Tannen, 1971), 349.] Figure 1.

Typical human-powered treadmill crane used in the construction of the Colosseum Source: http://www.the-colosseum.net/images/macchine.jpg All attendees at the Colosseum's events received tickets (made from pottery shards) with a number and the amphitheatre contained 80 separate general public entrances/exits marked with corresponding Roman numerals (as shown in Figure 2 below) that facilitated rapid seating and egress.[footnoteRef:13] According to one historian, "The entering and exiting of the Colosseum was methodically planned. There were eighty entrances at ground level.

Both entrances and exits were numbered, as was each staircase.

Four specific entrances were roped off for VIP guests."[footnoteRef:14] The reigning Roman emperor and the Vestal Virgins had the northern main entrance reserved for them and the other three entrances/exits were likewise reserved for the Roman elite[footnoteRef:15] As shown in Figure 2 below, the highly coveted entrances and exists that were reserved for the Roman elite were marked by their names or red numbers (as discussed further below).[footnoteRef:16] [13: Barbi, "The Colosseum," 37.] [14: Barbi, "The Colosseum," 38.] [15: Barbi, "The Colosseum," 38.] [16: Barbi, "The Colosseum," 38.] Figure 2.

Entrance/exit to the Colosseum marked by Roman numeral Source: http://www.italoamericano.org/ In 2013, a $285 million renovation project began on the Colosseum that has since revealed some other interesting facts about the amphitheater's entrances and exits, some of which have been discovered to have been painted in red numbers. According to staff writers at L'Italo-Americano, "[Red] numbers were painted on the arches to indicate the different sections of the amphitheater, very similar to a modern stadium.

Experts found out that the maximum visibility was obtained through the rubricatura technique, named after the ruben red color or by coloring the groove of each number."[footnoteRef:17] This coloration method served to ensure maximum visibility of the red-numbered entrances/exits and just four such portals, all placed on the structure's minor axes, have been discovered.

The small number of such specially reserved entrances and exits was likely due to the high political and social levels of the patrons that used them.[footnoteRef:18] [17: "The Colosseum renovation unveils a series of numbers in red paint," L'Italo-Americano [online] available: http://www.italoamericano.org/social/colosseum-renovation-unveils-series-numbers-red-paint, 3.] [18: "The Colosseum renovation unveils," 4.] Although estimates vary, modern researchers place the seating capacity of the Colosseum at about 50,000 spectators, but these spectators were carefully segregated according to social status.

In this regard, Barbi reports that, "As was the case with the distinctive entrances, special boxes were provided at the north and south ends respectively for the Emperor and the Vestal Virgins. Naturally, those seats had the best views of the arena.[footnoteRef:19] The seats between the emperor and the Vestal Virgins were reserved for Roman senators and some names of these attendees carved into the masonry can still be discerned as shown in Figure 3 below. [19: Barbi, "The Colosseum," 38.] Figure 3.

Roman senator's name carved into masonry at the Colosseum Source: http://www.acoupleontheroad.com/wp-content/uploads/2014/02/untitled-7-of-14.jpg Beneath the central area's ground level, the Roman engineers built a series of large rooms for human activities such as preparations for the events that would be held in the arena above as well as wild animal cages and various mechanical devices such as massive elevators to make gladiators, wild animals and scenery appear as if by deux ex machina-type magic in the middle of the central arena.[footnoteRef:20] In this regard, one historian reports that, "The arena floor was made of wooden planks supported by brick pillars; some sections of the floor were removable or could slide down the underground, so that the scenarios, animals and people could emerge from beneath."[footnoteRef:21] [20: "Technical description of the Colosseum," The Colosseum.

[online] available: http://www.colosseum.net / listingview.php?listingID=4] [21: "Description of the Colosseum," The Colosseum [online] available http://www.the-colosseum.net/architecture / descriptio_en.htm, 4.] In fact, one of the more interesting features of the Colosseum was the fact that much of the structure was located below ground. The arena's public area extended to 272 feet by 157 feet and was covered by a wooden floor and sand. The area beneath this arena floor was known as the hypogeum.

Although the wooden parts of the arena floor has essentially disintegrated over the centuries, the hypogeum remains visible today. According to Barbi, "The area consisted of a two-level subversive system of tunnels and cages where gladiators and animals were held before the contests began."[footnoteRef:22] It remains unclear, though, how a wooden floor covered with sand could withstand the pressure of millions of gallons of water purportedly used to stage naval battles in the Colosseum or prevent this water from flooding the hypogeum.

Given these necessities, it is reasonable to suggest that the Roman engineers also incorporated the same type of water-proof mortar to the main arena floor in order to impart these attributes, but again, the historical record is silent on this issue. Moreover, the precise function of the service tunnels that connect the main arena with the hypogeum remains unclear.

For instance, one historian emphasizes that, "Their function is uncertain; some say they housed archers who protected the spectators from the risk of wild animals reaching the public, some say they were latrines, and some say that there was a water channel meant to give supplementary protection from the beasts."[footnoteRef:23] [22: Barbi, "The Colosseum," 38.] [23: "Description of the Colosseum," 5.] In addition, there were also four additional levels above the central arena.

Each of these levels was likewise comprised of a series of stairways, rows of seats, passages and various rooms.[footnoteRef:24] According to one historian, "The upper floors were destined to the lower classes and women. The lowest floor was dedicated to prominent citizens."[footnoteRef:25] In addition, archways located on the second- and third-floor passageways feature statues of deities and well-known characters from Classical Roman mythology.[footnoteRef:26] [24: Barbi, "The Colosseum," 38.] [25: Barbi, "The Colosseum," 38.] [26: Barbi, "The Colosseum," 38.] An overhead view of the modern ruins of the Colosseum is provided in Figure 4 below.

Figure 4.Overhead view of the Colosseum today Source: http://www.colosseum.net/images/listing_photos/4_colosseum_4.jpg Some historians believe that the name, "Colosseum," is based on a "colossal" bronze statue of the Roman Emperor Nero that had stood near it.[footnoteRef:27] The Colosseum is located just east of the Roman Forum and construction began started between 70 and 72 AD during the reign of Emperor Vespasian for a very important reason: to ensure the popularity of the emperor at the time, a need that become especially acute following the rule of the widely despised Nero.[footnoteRef:28] For instance, according to Barbi, "The structure was to be a present to the Roman people and was to be constructed in the place where the previous Emperor Nero had built his residence, the Domus Aurea."[footnoteRef:29] [27: W.

H.

Goodyear, Roman and Medieval Art (New York: Grosset & Dunlap, 1897), 117.] [28: Barbi, "The Colosseum." 38.] [29: Barbi, "The Colosseum." 38.] At the time of Vespasian's death in 79 AD, construction on the Colosseum had progressed to the point where the third level had been completed.[footnoteRef:30] By 80 AD, though, Vespasian's son, Titus, succeeded in completing the top levels and the Colosseum was official dedicated to the people of Rome.[footnoteRef:31] In this regard, Sear advises that, "Vespasian was succeeded by his elder son, Titus, who in his short reign endeared himself to the Roman people as one of the best-loved Roman Emperors.

He inaugurated the Colosseum in AD 80."[footnoteRef:32] It is noteworthy, though, that the various events, including gladiatorial contests (known as munera) that were held at the Colosseum were sponsored by private Roman citizens rather than the Roman state.[footnoteRef:33] In this regard, Barbi reports that, "While every program contained a religious component, they were mostly organized to exhibit familial power and social status.

In fact, it was obligatory for the ruling class to coordinate the games in order to keep the citizens content as the munera were extremely well liked among the residents of Rome."[footnoteRef:34] [30: Barbi, "The Colosseum," 38..] [31: Barbi, "The Colosseum," 39.] [32: Frank Sear, Roman Architecture (London: Routledge, 1998), 144.] [33: Barbi, "The Colosseum," 38.] [34: Barbi, "The Colosseum," 38.] Despite its enormous size, the Colosseum's structure is completely self-supporting, a fact that is all the more impressive given the structure 6-acre foundation.

[footnoteRef:35] Although largely indiscernible from the overhead view shown in Figure 4 above, the Colosseum's outer wall is comprised of more than 3,000 feet of travertine stone that has been serious degraded over the centuries.

As can be readily seen in Figure 4 above, however, the north side of the wall of the Colosseum is still largely intact, but the current exterior of this wall is actually the original interior wall.[footnoteRef:36] [35: Barbi, "The Colosseum," 38.] [36: Barbi, "The Colosseum," 38.] Because the spectators in the Colosseum were exposed to harsh sunlight and other types of inclement weather during certain parts of the day, the amphitheater had an enormous awning known as the velarium.

This awning was manned by more than 1,000 Roman sailors who were well versed in rigging sails but the precise manner in which these coverings were deployed remains unclear, [footnoteRef:37] although the holes for the stanchions used to secure them are still visible today as shown in Figure 5 below. [37: "Technical description of the Colosseum," (2016) The Colosseum [online] available: http://www.colosseum.net / listingview.php?listingID=4, 5.] Figure 5.

Velarium socket and support Source: http://www.the-colosseum.net/images/supports.jpg The ingenious design of the velarium provided shade from the sun or protection from rain for as many as two-thirds of the Colosseum's spectators when it was fully deployed.[footnoteRef:38] [38: Barbi, "The Colosseum," 38.] The level above the senators was known as the maenianum primum and was reserved for higher ranking nobility and the next level, known as the maenianum secundum was reserved for blue-class workers; this sectin was divided into two parts: the lower part (known as the immum) was reserved for more well-to-do Roman citizens while the upper part (known as the summum) was set aside for less affluent citizens.[footnoteRef:39] During the reign of Domitian, the maenianum secundum in legneis level was added at the very top of the building.

Used for commoners, slaves and women, this was a "standing room only" area.[footnoteRef:40] [39: Barbi, "The Colosseum," 38.] [40: Barbi, "The Colosseum," 38.] Taken together, it is clear that the Colosseum represented a masterful work of engineering that included numerous innovations that would become the standard by which all other stadia would be thereafter measured.

As one modern historian suggests, "The Colosseum is not just an architectural masterpiece, but in terms of planning, engineering and organization it must rank as one of the most astonishing achievements of antiquity."[footnoteRef:41] Moreover, the Colosseum was just part (albeit the major part) of a larger complex of buildings that included housing for the Roman sailors tasked with maintaining the velarium and the gladiators who were scheduled to fight as well as eateries and public baths.

According to Barbi and like-minded historians, these attributes set the Colosseum apart from other ancient Roman works: "One cannot but marvel at the creators of such a complex."[footnoteRef:42] [41: Barbi, "The Colosseum," 38.] [42: Sear, Roman Architecture, 144.] By contrast, some architectural scholars during the late 19th century characterized the Colosseum as being poorly designed from the outset.

For instance, writing in 1888, Burn argues that, "As specimens of architecture, the amphitheatres are more remarkable for the mechanical skill and admirable adaptation to their purpose displayed in them, than for any beauty of shape or decoration. The hugest of all, the Coliseum, was ill proportioned and unpleasing in its lines when entire."[footnoteRef:43] Unlike Greek temples that were designed to be aesthetically pleasing to the eye, Burn maintains that the architecture of the Colosseum is overrated.

In this regard, Burn adds that, "The solid wall of its uppermost story gave it a heavy appearance; the width of the whole mass is too great in proportion to its height; and the columns and entablatures with which its exterior is decorated are structurally false, as they afford no real support to the building."[footnoteRef:44] [43: Robert Burn, Roman Literature in Relation to Roman Art (London: MacMillan,1888), 277.] [44: Burn, Roman Literature, 277.] Conversely,.