Why Is the Colosseum Broken? The Real Reasons It Fell Into Ruin

Updated for 2026 · 5 min read

Stand in front of the Colosseum and the first thing you notice is that half of it is missing. One side soars to its full original height; the other looks like it was bitten off. So why is the Colosseum broken, and what actually happened to it? The short version: earthquakes knocked it down, and Romans carried it away. Here is the full story.

1. Earthquakes did the heavy damage

Rome sits in a seismically active region, and the Colosseum has weathered repeated earthquakes over nearly 2,000 years. Tremors in 443 and 1231 cracked and weakened the structure, but the decisive blow came with the great earthquake of 1349. It brought down the entire southern outer wall in one catastrophic collapse.

Why only the south side? Because that flank sat on softer, made-up ground — part of the site was reclaimed from the drained lake of Nero's palace — while the surviving northern wall rests on more stable bedrock. The same quake that flattened the south left the north standing at its original height, which is exactly why the building looks so lopsided today.

2. Romans quarried it for stone (spoliation)

Here is the part most people don't realise: much of the Colosseum wasn't lost — it was recycled. Once the gladiatorial games ended in the 6th century and the building fell out of use, it became, in effect, a giant quarry in the middle of Rome. For centuries, builders helped themselves to its ready-cut travertine.

Colosseum stone was reused in landmark Roman buildings including parts of palaces, churches, bridges and St Peter's Basilica. This practice of stripping old monuments for new construction is called spoliation, and the Colosseum was its most famous victim. The looting only really stopped in the 18th century, when the Church declared the arena a sacred site tied to Christian martyrs and began protecting it.

3. The iron clamps were dug out

Look closely at the facade and you'll see it is peppered with holes. The Romans joined the travertine blocks not with mortar but with about 300 tonnes of iron clamps. In the metal-hungry Middle Ages, scavengers chiselled out those clamps to melt down and reuse — and every hole you see is one they prised open. Removing the clamps also made the structure weaker and more prone to further collapse.

4. Fire, lightning, floods and neglect

Earthquakes and looting did the most, but they had help. The Colosseum was struck by fires and lightning (a serious fire after a lightning strike in AD 217 destroyed the wooden upper levels and forced years of repairs), battered by floods from the nearby Tiber, and choked by vegetation that rooted in the stonework during centuries of abandonment. Through the medieval period it was even repurposed as a fortress and housing, then left to decay.

So how much is actually gone?

Roughly two-thirds of the original Colosseum has been lost. What survives is still enough to make it one of the most recognisable buildings on earth — and modern restoration since the 1990s has stabilised the structure, cleaned the facade, and reopened areas like the arena floor and the hypogeum beneath it. If anything, knowing what it has survived makes standing inside it even more remarkable. For how it was put together in the first place, see our guide to Colosseum architecture.