A Building Engineered for Eternity
Construction began in 72 AD under Emperor Vespasian and was completed in 80 AD under his son Titus. The scale of the undertaking was genuinely staggering. The outer wall alone required roughly 240,000 loads of stone carted in from quarries twenty miles away, partly on roads specially built for the purpose.
The outer walls, which top off at about 48.5 meters, have three levels of arches framed by columns topped by capitals of the Ionic, Doric, and Corinthian orders. Emperor Domitian later added the underground hypogeum and upper tiers between 81 and 96 AD.
What Is Actually Gone
What’s missing today – roughly two-thirds of the original outer wall – tells its own story of destruction and survival. The loss is concentrated almost entirely on one side of the building, which makes the asymmetry all the more dramatic when you see it in person.
The south-facing outer ring collapsed almost completely, largely because that side of the building rested on softer, less stable alluvial soil compared to the firmer ground on the north side, which is why the north wall has survived largely intact while the south side is gone. That geological difference, invisible to visitors for centuries, would ultimately define the shape of the ruin we see today.
The 1349 Earthquake: The Single Biggest Blow
Major earthquakes in 443 AD and 1349 AD caused significant structural damage – the 1349 quake collapsed the entire southern outer wall. By that point, the building had already been weakened by centuries of neglect and material removal, so the ground had less resistance to offer when the tremors arrived.
The main reason the Colosseum is half missing is because of a large earthquake that struck Rome in 1349. Because the Colosseum was already in bad shape by that point, the earthquake caused the entire outer side of the south end to collapse. The south side stood on weaker ground, came down in 1349, and its fallen stone was then quarried for travertine into the eighteenth century.
The Medieval Quarry: Centuries of Stone Removal
Starting in the medieval period and accelerating through the Renaissance, popes, noble families, and builders systematically stripped the Colosseum for reusable material. This was not chaotic looting in the shadows – it was organized, permitted, and profitable.
Starting in the Middle Ages, popes granted licenses to quarry materials from the Colosseum. In 1452 alone, one contractor removed 2,522 cartloads of material. That single statistic gives a sense of the industrial scale of what was happening to one of Rome’s most important ancient structures.
Though the amphitheater was still in use at the beginning of the 6th century, it was now oversized for the reduced population of the city, so the Romans started recycling its materials. Everything was recycled: the thick marble slabs that lined the walls, tuff blocks, the lead of the piping, and the metal grips that kept the travertine blocks together, even the bricks.
Where the Stone Actually Went
The travertine and marble from the Colosseum were used to build some of Rome’s most famous landmarks: St. Peter’s Basilica, Palazzo Venezia, Palazzo Barberini, the Basilica of San Giovanni in Laterano, and the Palazzo della Cancelleria. In a very real sense, visiting Rome means encountering pieces of the Colosseum scattered across the entire city.
The travertine stone blocks were removed from the Colosseum and reutilized to build church facades and private buildings. For example, the travertine stone of the Colosseum ended up in the facade of the church of Sant’Agostino near the Pantheon and in Palazzo Barberini near Piazza Barberini.
Records show travertine stone from the building was put up for sale as early as 1362. Pope Pius II even had a wagon purpose-built to move Colosseum stone to Palazzo Venezia. The trade in Colosseum materials was, at times, quite literally official city business.
The Iron Clamps: A Hidden Layer of Damage
During construction, Roman engineers used thousands of iron and bronze clamps to secure the massive travertine blocks without the need for mortar. This was a clever and durable building technique – until the metal itself became more valuable than the stone it was holding together.
The iron clamps that originally held the travertine blocks together were pried out and melted down for reuse, leaving behind the pockmarked holes still visible in the stonework today. Historians report that it was probably during the Gothic War that most of the metal grips were systematically removed.
The removal of these clamps significantly weakened the Colosseum. Out of everything done before the year 1349, it was the removal of the iron clamps that held the stones together which remains one of the key reasons the Colosseum is half missing. Without those clamps, the blocks had far less resistance against the lateral forces that earthquakes generate.
Fire, Lightning, and Earlier Damage
One contributing factor to the Colosseum’s vulnerability is a lightning strike in 217 AD which started a massive fire in the structure. Historians have theorized that this fire drastically affected the structural integrity of the Colosseum, and it would not be fully repaired until 320 AD.
By the time the medieval stone-strippers arrived, they were working on a building that had already endured fire, at least two major earthquakes, centuries of heavy use, and declining maintenance. The Colosseum’s deterioration was not a single event. It was an accumulation.
The Law That Came Too Late
During the Renaissance, humanists such as Pope Eugene IV called for the historical remains to be preserved. However, this did not prevent the building from being used as a quarry supplying stone for great Renaissance buildings such as the Vatican’s St. Peter’s church.
Real conservation of the Colosseum did not begin until the seventeenth and eighteenth centuries. A law was passed in 1743 forbidding any further removal of stone. By then, the damage was largely done. The law arrived after roughly a thousand years of extraction had already reshaped the building.
What the Damage Accidentally Revealed
Today’s visitors see roughly one-third of the original outer wall on the north side, largely intact, alongside the dramatic cross-section of the interior exposed by the 1349 collapse – which, somewhat ironically, is what allows visitors to see the hypogeum and the tiered seating structure so clearly.
The outline of the Colosseum as it exists now is the product of two different forces acting on two different halves: deliberate preservation on one side, geology plus the stone trade on the other. It’s one of those rare cases where destruction and survival exist right next to each other, separated by a few hundred meters of ancient engineering.
Restoration Efforts in the 21st Century
Restoration efforts in 2026 focused on the southern side of the ancient oval-shaped arena, led by Stefano Boeri Interiors, a multidisciplinary design studio based in Milan. The restoration design was based on an analysis of the Colosseum’s northern facade, where the original elements were intact, and archaeological investigations conducted by the Parco Archeologico del Colosseo.
A passage within the structure was restored using EU recovery funds and Parco Colosseo resources in a project completed between October 2024 and September 2025, opening to visitors on 27 October 2025. A second restoration phase is planned for 2026, targeting an additional section not yet open to visitors, with the aim of recovering stucco and fresco fragments from the original decoration.
The materials unearthed in recent excavations are now the focus of a new exhibition section in the hypogeum, inaugurated in July 2025. At the same time, a project for a new arena is under way – a light, reversible, partially movable structure designed to restore the amphitheater’s original configuration while allowing continued access to the underground areas.
The Takeaway
The missing wall of the Colosseum is not simply a wound – it’s a record. Every absent stone, every pockmarked cavity where an iron clamp once sat, and every arch that crumbled into the soft southern soil tells part of a story that spans more than a thousand years. The building was quarried to build churches, palaces, and piazzas that Romans still live alongside today.
What remains standing is genuinely impressive. What’s gone tells the more complicated story: of a city that consumed its own past to build its future, and only gradually came to understand what it had lost. The Colosseum endures not in spite of its incompleteness, but partly because of it. That exposed interior, that asymmetric silhouette, that raw southern edge – they are the reason visitors still feel something when they stand in front of it.
AI Disclaimer: This article was created with the assistance of AI tools and reviewed by a human editor.