The Colosseum

THE COLOSSEUM Rome, Italy · 70–80 CE · Roman Imperial AT-RISK

SITE AT A GLANCE Location: Piazza del Colosseo, Rome, Lazio, Italy Country: Italy Region: Southern Europe / Mediterranean Coordinates: 41.8902° N, 12.4922° E Type: Built Heritage Sub-types: Monumental Architecture, Imperial Infrastructure Period: Constructed 70–80 CE; active through 6th century CE Risk Level: At-Risk Risks: Mass tourism, Air pollution, Seismic vulnerability, Urban vibration, Acid rain, Climate change UNESCO Status: Inscribed 1980 (Historic Centre of Rome)

3D DOCUMENTATION A 1.5-million-triangle drone photogrammetry scan of the Colosseum's exterior is available on Sketchfab under a CC-BY licence, produced by Brian Trepanier (@CMBC). The model captures the travertine surface in high resolution and is freely downloadable. Additional documentation is held by CyArk through the Open Heritage 3D programme at openheritage3d.org. Europeana hosts thousands of digitised historical drawings, engravings, and photographs through europeana.eu. Sketchfab model: https://sketchfab.com/3d-models/colosseum-rome-italy-535dc96e586f40bd956ea3cbff810055 Open Heritage archive: https://openheritage3d.org UNESCO dossier: https://whc.unesco.org/en/list/91

SITE DESCRIPTION The Colosseum rises four storeys above the heart of Rome — 48.5 metres of travertine limestone, tuff, brick, and Roman concrete enclosing an elliptical arena 83 by 48 metres. It is the largest amphitheatre ever constructed, built between 70 and 80 CE using approximately 100,000 cubic metres of travertine held together by 300 tonnes of iron clamps, the holes left by their medieval removal still visible as a kind of negative archaeology on every façade. The structure held between 50,000 and 80,000 spectators, arranged in tiers that corresponded precisely to their social rank. Below the arena floor lay the hypogeum, a network of tunnels, animal cages, and counterweighted lift platforms connected to the surface by eighty vertical shafts through which animals, scenery, and gladiators could be hoisted into the combat zone in seconds. A vast retractable awning, the velarium, operated by naval sailors, shaded the entire crowd from the Roman sun. The Venerable Bede wrote in the eighth century that while the Colosseum stands, Rome shall stand, and when Rome falls, the world. Two thousand years on, six million people a year still come to confirm that it is still standing.

HISTORICAL SIGNIFICANCE The Colosseum was built on the site of Nero's private lake — an act of political symbolism that deliberately reclaimed imperial excess for the Roman people. Vespasian began it; his son Titus inaugurated it in 80 CE with one hundred days of games in which nine thousand animals were reportedly killed. The spatial hierarchy of the seating was itself a statement of social order encoded in stone. Every class of Roman society was assigned its position in the building, from the emperor in his box to the slaves at the very top, and the building communicated that order every time it filled. The gladiators who fought there were mostly enslaved people, prisoners of war, or condemned criminals, though some were free volunteers drawn by pay and celebrity. The animals shipped from Africa and Asia — lions, elephants, rhinoceroses, hippopotamuses, ostriches — came at a cost to the ecology of North Africa that is only now fully appreciated. Lion and elephant populations that had been widespread across the continent were functionally eliminated from large parts of their range by the demand of the Roman games. The engineering innovations introduced at the Colosseum — the systematic use of the arch, the vault, and Roman concrete — became the template for public architecture across the Western world for two millennia. Every stadium built since, from Victorian cricket grounds to contemporary football arenas, is in some architectural lineage from this building.

THE STORY OF THE SITE

70 to 80 CE: Construction and Inauguration Emperor Vespasian begins construction in 70 CE on the site of Nero's private lake, using Jewish prisoners captured in the First Jewish-Roman War as the primary labour force. His son Titus completes and inaugurates the building in 80 CE with one hundred days of games. Emperor Domitian adds the fourth storey and completes the hypogeum underground network in 82 CE, establishing the form the Colosseum will maintain for centuries.

80 CE to 523 CE: The Games For nearly five centuries the Colosseum operates as the centre of Roman public entertainment, hosting gladiatorial contests, animal hunts, public executions, and in its early years staged naval battles for which the arena was flooded. The last recorded gladiatorial games are held in 523 CE, under the Ostrogothic King Theodoric. The wealth required to sustain the spectacles has disappeared with the Western Roman Empire.

6th Century to 18th Century: Spoliation and Repurposing After the games end, the Colosseum is repurposed across centuries as a fortress by rival noble families, then as workshops, housing, and a cemetery. Between the 12th and 19th centuries it becomes Rome's greatest quarry: travertine stripped from its façades is used in the construction of St Peter's Basilica, Palazzo Venezia, and countless other buildings across the city. The holes left by the removal of the iron clamps are the fingerprints of this sustained disassembly. Pope Benedict XIV consecrates the site in 1749 in memory of Christian martyrs — the historical accuracy of which scholars debate — halting the worst of the spoliation.

19th Century to Present: Archaeology and Conservation Systematic archaeological excavation begins in the 19th century, clearing the hypogeum for the first time since antiquity. The 20th and 21st centuries bring successive restoration campaigns, the most significant of which, a €25 million programme partly funded by the luxury brand Tod's and completed in 2016, reveals the original pale stone colours beneath centuries of pollution. A reconstruction of the arena floor, removed in the 19th century to expose the hypogeum, is currently in progress. A wooden floor is being installed in phases to restore the original spatial experience.

THREATS AND RISK ASSESSMENT Pollution Vehicle exhaust, particulate matter, and sulphur dioxide from Rome's traffic corrode the travertine stone and blacken surfaces that were originally white and ochre. The 2016 restoration cleaned the exterior and revealed original stone colours, but pollution begins to reaccumulate immediately after each cleaning. There is no permanent solution available that does not require changes to urban traffic patterns that successive Italian governments have proven unwilling to mandate.

Seismic Vulnerability Rome sits in a seismically active zone. A severe earthquake in 1349 collapsed the entire south outer wall, whose stone was immediately quarried for construction elsewhere. The Colosseum's current structural condition — centuries of repairs, modifications, and material losses — makes it more vulnerable to seismic events than its original construction was. A structural seismic assessment programme is needed but has not been completed.

Tourism Pressure Six million annual visitors generate physical stress on the structure, microclimate changes within enclosed spaces, and management challenges that the site's infrastructure was never designed to handle. Queue management, ticketing, and visitor flow controls are ongoing concerns. The Parco Colosseo authority, which manages the site, is attempting to address these challenges with phased ticketing and timed entry, with mixed success.

RESEARCH AND SCHOLARLY CONTEXT The Colosseum is among the most thoroughly documented ancient structures in existence. The Parco Colosseo authority publishes annual conservation reports, and the UNESCO World Heritage dossier for the Historic Centre of Rome provides the most authoritative condition assessments available. CyArk's Open Heritage programme has produced photogrammetric documentation of the exterior and key interior sections. The 1.5-million-triangle drone scan on Sketchfab, available under CC-BY licence, allows researchers and educators worldwide to study the building's geometry without being present in Rome. Europeana hosts thousands of historical images and archival documents relating to the Colosseum's post-antique history and its role in Western cultural imagination.

IF NOTHING CHANGES The Colosseum is not at risk of sudden collapse. What is at risk is the slow, cumulative deterioration of the travertine surface under sustained pollution, the loss of structural integrity through inadequately managed seismic risk, and the degradation of the visitor experience and the physical fabric of the site through the daily pressure of six million annual visitors. These are manageable threats with adequate resources and political will. The Colosseum has survived emperors, earthquakes, medieval quarrying, and two world wars. The question is whether it will survive the particular pressures of the twenty-first century: mass tourism, atmospheric pollution, and the institutional fatigue that comes from managing the world's most famous ruin while Rome's traffic circles it every day.