How the Colosseum Was Once Turned Into a Fortress

The Colosseum is so strongly associated with gladiators that its later history can feel almost impossible to picture. Yet centuries after the last great public spectacles, Rome’s enormous amphitheatre was no longer functioning as an arena. Its vaults became homes, workshops, storerooms, animal shelters, and rented commercial spaces—and one powerful baronial family converted part of it into a fortified residence.

The surprising truth: the medieval Colosseum was not simply an abandoned ruin, and it was not wholly transformed into one enormous castle. It became a densely reused urban complex in which domestic life, trade, religion, livestock, scavenging, and elite military power could occupy the same ancient structure.

From imperial arena to inhabited ruin

The Flavian Amphitheatre did not become empty overnight when the Western Roman Empire weakened. Its ancient entertainment role declined gradually, with the last documented spectacle taking place in the early sixth century. As organized games disappeared, the building entered a long period of adaptation rather than simple abandonment.

Earthquakes, missing maintenance, the removal of valuable materials, and the loss of parts of the original structure changed what could be used. The timber-covered arena floor vanished, exposing or filling sections of the underground service complex. Outer galleries suffered collapses. Marble, metal fittings, and reusable stone were taken away. Even so, the surviving concrete vaults and corridors remained extraordinarily useful.

By the medieval period, people were living and working within the amphitheatre. Official archaeological research identifies domus, or residences, alongside spaces known as cryptae. These reused rooms could function as warehouses, stables, sheds, temporary lodging, or shops. Excavations have revealed practical features such as hearths, plastered counters, animal troughs, and loft arrangements for storing hay.

The Frangipane family builds a fortress

In the twelfth century, the Frangipane—one of medieval Rome’s influential baronial families—established a fortified complex within the Colosseum. The earliest surviving evidence dates to 1133, but the project was far more specific than the claim that the entire amphitheatre became a castle.

The documented fortress occupied 11 arcades across the first and second levels on the northeastern side. This position offered broad visibility from the Velian ridge toward the Caelian Hill. The complex included a defensive tower at the amphitheatre’s ancient eastern entrance and a wooden patrol walkway, or chemin de ronde, running along part of the southern face.

The wood has disappeared, but its attachment points have not. Beam sockets that supported the projecting walkway can still be identified along the top of the inner ring on the first level. These small architectural scars are some of the clearest physical reminders that medieval builders inserted a defensive system into Roman masonry more than a thousand years after the amphitheatre was constructed.

Why the location mattered

The Frangipane did not choose the Colosseum simply because it was enormous. Medieval Rome was divided among rival families whose fortified residences formed networks of political and military control. Ancient monuments were often absorbed into those networks because they offered height, masonry, visibility, and command over important routes.

The Colosseum’s position was especially valuable. According to the Archaeological Park of the Colosseum, the Frangipane defensive zone helped control territory extending from the Forum and Palatine area, through the Colosseum valley, toward the entrance to the Lateran Palace—the principal papal residence during much of the Middle Ages.

This is why the fortress should be understood as part of a wider urban system. The Frangipane also incorporated or controlled other ancient structures in the area. Their power was expressed through a chain of defensible buildings rather than through one isolated castle surrounded by open countryside.

What daily life may have looked like

The evidence lets us reconstruct the Colosseum’s medieval atmosphere more confidently than its private conversations. Archaeologists have identified living quarters, hearths, counters, troughs, storage arrangements, and spaces used by animals and craftspeople. Documents also record leased residential and working areas between the eleventh and thirteenth centuries.

That does not mean every vaulted room had the same purpose, or that the entire amphitheatre was organized by one landlord. Uses changed over time. A chamber might serve as a shop in one period and storage in another. Larger dwellings could extend over one or two floors and include porticoes or vegetable gardens, while more modest spaces supported trade, livestock, or temporary lodging.

The Annibaldi take control

Baronial control in medieval Rome was rarely permanent. During the thirteenth century, the Frangipane lost their Colosseum fortress to the rival Annibaldi family. The Annibaldi remained associated with the property until the late fourteenth century.

This transfer shows that the fortified Colosseum was not merely an eccentric residence. It was valuable enough to be contested by major aristocratic families. Its strategic role, however, declined as Rome’s political geography changed and as the monument suffered further damage.

Earthquakes, quarrying, and a changing monument

The fortress period unfolded inside a building that had already endured centuries of damage. Earthquakes in 847 and 1349 were particularly important, although historians and engineers are cautious about assigning every visible collapse to one event. The medieval amphitheatre was also repeatedly stripped of reusable materials.

Stone removed from the Colosseum entered later Roman building projects, while iron clamps and decorative materials were extracted wherever possible. This quarrying was destructive, but it also reflects a premodern attitude toward ruins: ancient buildings were often treated as practical reserves of worked stone rather than as untouchable archaeological monuments.

The official archaeological park notes that the Colosseum continued to be used as a source of materials into the mid-eighteenth century. By then, however, papal authorities increasingly sought to protect and Christianize the structure. In 1744, Pope Benedict XIV issued an edict against its desecration; for the Jubilee of 1750, he consecrated the arena and ordered the construction of Stations of the Cross.

Can visitors still see the fortress today?

The medieval tower and timber walkway no longer survive as a complete castle-like installation, so casual visitors may walk past the evidence without realizing what it represents. The most specific surviving traces are the cavities that once held the walkway’s projecting wooden beams.

Visitors may also encounter masonry changes, reused openings, and alterations from many phases of the Colosseum’s long history. These should be interpreted carefully: not every blocked arch or patch of brick belongs to the Frangipane fortress. The monument is a layered structure shaped by Roman construction, ancient repairs, medieval reuse, earthquakes, quarrying, religious additions, excavations, and modern conservation.

• Look upward Beam sockets connected with the medieval walkway survive along the inner ring of the first level.
• Read the structure Notice how vaults, corridors, and entrances could be divided into independent spaces for homes, shops, storage, and defense.
• Use official guidance Current routes, closures, tickets, and restoration information can change, so consult the archaeological park before visiting.

Why this chapter matters

The fortress story changes the way we think about historical survival. The Colosseum did not pass directly from imperial arena to protected tourist attraction. It remained useful for very different communities: renters, artisans, clergy, animals, aristocrats, builders, pilgrims, excavators, conservators, and visitors.

Its survival was not the result of uninterrupted preservation. Parts endured because the structure could be adapted; other parts disappeared because they were useful as raw material. The same monument could be home, workplace, stable, fortress, quarry, shrine, archaeological site, and national symbol at different moments—or sometimes at the same moment.

That layered history is precisely why UNESCO describes Rome’s historic centre as a place of exceptional architectural and urban stratification. The Colosseum is not only evidence of imperial engineering. It is also evidence of how later societies negotiated, reused, damaged, defended, sanctified, studied, and eventually protected the ancient city around them.

The next time you picture the Colosseum, keep the gladiators—but add medieval renters tending hearths beneath the seating, livestock moving through old corridors, craftspeople working inside Roman vaults, and a baronial family guarding a timber walkway above them. Same amphitheatre. Entirely different Rome.