CitiesItaly
The missing half of the Colosseum is not missing. For roughly a thousand years ancient Rome was treated as a quarry, and the popes worked it: marble, lead and iron came out of the amphitheatre and went into St Peter's, Palazzo Venezia, Palazzo Barberini and the Cancelleria. The extraction only stopped in the eighteenth century, when Benedict XIV consecrated the ruin to Christian martyrs. Most of the Renaissance Rome people come to admire is an older Rome, taken apart.
The first-century amphitheatre, and the single clearest illustration of what Rome did to itself. The reason one side stands full height and the other is sheared away is not earthquake damage alone; it was mined for building stone from the fifteenth century onward. Look for the pockmarks across the remaining travertine, holes left where iron cramps were levered out to be melted down.
The best-preserved building of ancient Rome, and it survived precisely because it stopped being a Roman temple. Consecrated as a church in the seventh century, it acquired a protector at exactly the moment other monuments were being dismantled. Its concrete dome, unreinforced and nearly two thousand years old, is still the largest of its kind anywhere.
Built as Hadrian's mausoleum, converted into a fortress, then a papal refuge connected to the Vatican by a walled escape corridor. It is the reuse principle in a single structure: an emperor's tomb turned into the thing that kept popes alive during sieges. The corridor, the Passetto di Borgo, runs along the top of a wall you can still trace on foot.
The centre of the Catholic Church, rebuilt across the sixteenth and seventeenth centuries on the site of a fourth-century basilica. The relevant fact for this page is where its material came from: travertine taken out of the Colosseum went into the square and the loggia. The building that best represents papal Rome is partly made of imperial Rome.
A church built inside the frigidarium and tepidarium of the Baths of Diocletian, adapted by Michelangelo at the age of 86. He did not clear the site and start again; he left the Roman hall, over ninety metres of it, structurally untouched and put a church inside it. The apse occupies the natatio, the baths' open-air cold pool.
The civic centre of the ancient city, and for centuries afterwards a cattle pasture known as the Campo Vaccino, buried under metres of its own debris. What you walk through was substantially excavated in the nineteenth and twentieth centuries. The ground level you see is not the level Romans walked; the city rose on top of itself before anyone dug back down.
A twelfth-century basilica built over a fourth-century church, built over a Roman house and a temple to Mithras. You can descend through all of it. This is the whole thesis of Rome in one staircase: nothing was cleared away, it was simply built upon, and the older city is still down there holding the newer one up.
The baroque fountain everyone photographs, finished in 1762, and fed by the Aqua Virgo, an aqueduct commissioned in 19 BC. That is the detail worth carrying: the spectacle is eighteenth century, the water delivery system running it is two thousand years old and has never entirely stopped working.
Four republican-era temples sunk below modern street level, uncovered during 1920s demolition work rather than sought out. It is also, by the best reckoning, where Caesar was killed, the Curia of Pompey having stood alongside. For decades its most visible residents were a colony of stray cats, which is genuinely how most Romans think of the site.
A fifteenth-century cardinal's palace on the piazza of the same name, later Mussolini's offices, its balcony the one he made speeches from. It belongs on this list for its stone: travertine quarried out of the Colosseum went into building it. Rome's habit of recycling itself did not stop at churches.
The Colosseum is half-missing because Rome mined it for a thousand years.
From the fifteenth century onward it served as a quarry for marble, travertine, lead and iron, feeding St Peter's, Palazzo Venezia, Palazzo Barberini, the Cancelleria and San Giovanni in Laterano. The sacking stopped only when Benedict XIV consecrated the site in the eighteenth century.
The Pantheon survived by converting.
It is the best-preserved building of ancient Rome because it was consecrated as a Christian church in the seventh century, which gave it an owner with reason to maintain it at precisely the point when other pagan monuments were being stripped for parts.
The Trevi Fountain is baroque scenery bolted onto a Roman aqueduct from 19 BC.
The Aqua Virgo was completed in 19 BC and this site has been a water source ever since. Nicola Salvi won the design competition in 1730 and died before the fountain was finished; it was finally inaugurated in 1762, seventeen centuries after the water supply it decorates.
Michelangelo, aged 86, built a church inside a Roman bathhouse without altering it.
Santa Maria degli Angeli occupies the frigidarium and tepidarium of the Baths of Diocletian. He worked within the existing Roman hall rather than demolishing it, and used the natatio, the open-air cold pool, as the apse. The ceiling above you is Roman engineering, not Renaissance.
The Roman Forum spent centuries as a cow field.
Buried under its own accumulated debris, the civic heart of the ancient world was known as the Campo Vaccino, the cattle field, and was grazed as such. Systematic excavation back down to the ancient level is a nineteenth and twentieth-century project.
The pope had a walled corridor for running away.
The Passetto di Borgo links the Vatican to Castel Sant'Angelo, a fortress that began life as Hadrian's mausoleum. It was used in earnest, most famously during the 1527 Sack of Rome.
You can walk down through four centuries in one building.
San Clemente stacks a twelfth-century basilica on a fourth-century church on a Roman house and a Mithraic temple, all accessible by descending staircases. Rome did not clear its old buildings away; it used them as foundations.
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