How much, in modern dollars, did the Colosseum cost to build?
And how much would it cost to build an exact replica today?
We’ll start with the first question.
The Romans reckoned costs in sestertii, big brass coins worth a quarter of a denarius.
At the time the Colosseum was built, one sestertius could buy two loaves of bread, four cups of
cheap wine, or a single cup of good wine.
A tunic cost about 15 sestertii, and the rent for a decent apartment was probably between
300-500 sestertii a year.
The average annual wage for an unskilled laborer was around 1,000 sestertii.
A marble mausoleum along the Via Appia could easily cost 10-20,000 sestertii.
A wealthy senator could spend 300,000 adding a private bath to his house.
Simply finishing Nero’s Golden House cost 50,000,000 sestertii.
How did the Colosseum compare?
Since no literary source or inscription provides any clues, we have to estimate on the basis
of labor and material costs.
The first task of the Colosseum’s builders was to excavate the foundation trench, as
large as the building’s footprint and more than 8 meters deep.
Removing something like 170,000 cubic meters of earth and stone was an enormous task, involving
thousands of workers.
Contrary to what you might assume, few of them were slaves: although the private contractors
who built the Colosseum had small permanent staffs of skilled slaves and freedmen, most
of the work was done by unskilled day laborers.
Following an approach pioneered by Janet DeLaine, a professor of Roman archaeology at Oxford,
I used a nineteenth-century construction manual to estimate the labor required to clear the
Colosseum’s foundation trench with hand tools.
If I did the math right, something like 70,000 man-days of labor would have been required
to excavate and haul away 170,000 cubic meters of rocky soil – but this does not account
for the fact that the workmen had to cut into bedrock on the north side of the foundation
trench, and had to contend with a high water table throughout.
So let’s say, conservatively, that 125,000 man-days of labor were required.
I’ll assume that the workmen earned an average of 4 sestertii a day, which seems to have
been the going rate for a laborer in first-century Rome.
By that reckoning, the cost of clearing the Colosseum’s foundation trench was in the
neighborhood of 500,000 sestertii.
Next, the foundations were laid.
Like the building above it, the Colosseum’s foundation was a huge ellipse about 60 meters
wide.
It consisted of two parts: a lower foundation of solid concrete 7 meters thick, and a 6
meter thick upper foundation, also concrete, honeycombed with service passages.
Roman concrete, as I’ve discussed in some of my other videos, was not poured like modern
concrete, but spread in courses.
First, retaining walls of brick or stone were constructed as a sort of form.
A layer of coarse aggregate – in the Colosseum’s case, chunks of basalt and tufa – was laid
down between these walls, and pozzolana mortar was troweled over the rubble bed, almost dry.
The mixture was then pounded firm with wooden mallets.
Besides its strength and durability, Roman concrete had the great virtue of being cheap.
All the materials were available locally; and – unlike masonry – a large concrete
structure could be built largely with unskilled labor.
By my best estimate, the upper and lower foundations together used roughly 250,000 cubic meters
of rubble and concrete.
Again following Janet DeLaine, who wrote an article on the relative costs of different
types of Roman construction, I estimate that each cubic meter of concrete cost the equivalent
of 10 days’ wages for a laborer.
By our equation, that gives a total of about 10,000,000 sestertii for the foundation.
Next, work began on the superstructure.
Although most large Roman buildings were made of brick-faced concrete, both the perimeter
wall and the interior support columns of the Colosseum were built with massive blocks of
travertine, quarried at Tivoli and ferried to Rome by barge.
The Colosseum required about 100,000 cubic meters of travertine – roughly one-fiftieth,
incidentally, of all the travertine ever quarried by the Romans.
The stone, cut into blocks with an average weight of four tons, was lifted into place
by simple treadwheel cranes like the one pictured in this relief, and clamped with 300 tons
of iron.
Travertine is a hard and heavy stone, difficult to work and transport.
It was correspondingly expensive.
Each cubic meter, by DeLaine’s estimate, cost the equivalent of 100 days’ wages for
a laborer.
The basic cost would have been amplified by the fact that each block had to be lifted,
sometimes as much as 50 meters, by muscle power.
Iron was also much more expensive than it is now.
So let’s say that building the travertine components of the Colosseum cost 50,000,000
sestertii.
Although the key structural elements of the Colosseum were travertine, the vaults and
substructures under the seats used roughly 100,000 cubic meters of tufa and concrete.
Tufa – a soft volcanic stone – was considerably less expensive than travertine, and concrete,
as we’ve seen, was cheaper still.
The relative economy of the materials, however, was partially offset by the complexity of
constructing so many vaults, ramps, and passageways.
So I think that 20,000,000 sestertii is a reasonable guess for the cost of the substructures
and passageways.
Except for the uppermost tier, which had wooden benches, the seats of the Colosseum were made
of Carrara marble.
Although this was one of the least expensive varieties of marble, it still cost far more
than travertine, perhaps the equivalent of 150 laborer-days per cubic meter.
I’ve never seen any estimate for the amount of marble used in the Colosseum.
The lowest tier of seats, the Senatorial podium, was built entirely of marble; the seats above
had brick substructures faced with marble slabs.
On that basis, I’ll say, more or less arbitrarily, that 5,000 cubic meters of marble were used
throughout the building.
If that number is anything like correct, the cost of the marble would have been around
3,000,000 sestertii.
The corridors of the Colosseum were plastered, painted, and equipped with lead pipes for
water fountains.
More than 150 life-size statues stood in the arches of the upper stories, and imposing
quadriga groups crowned the main entrances.
The statues alone, to judge from attested prices, would have collectively cost well
over a million sestertii.
Without attempting to estimate the expense of each component, I think it’s reasonable
to suggest total finishing costs in the neighborhood of 2,500,000 sestertii.
So: how much did it cost to build the Colosseum 19 centuries ago?
Adding up the estimates I’ve given to this point brings us to 86,000,000 sestertii.
This, I suspect, is still too low, since basic estimates on the basis of material fail to
account for the many challenges of constructing a building on the Colosseum’s scale.
So let’s say, just to have a nice round figure we can work with, that construction
cost something on the order of 100,000,000 sestertii.
This was a lot of money.
The average annual income for a Roman laborer was around 1,000 sestertii.
Imperial Roman senators, who were required to own property worth at least 1,000,000 sestertii,
were very wealthy men.
The two richest Romans known to us were worth 400,000,000 sestertii – four times the estimated
cost of the Colosseum.
But if my estimate is anything like correct, the Colosseum was far from the most expensive
building project in Rome.
Domitian reportedly spent nearly 300 million sestertii just gilding the roof and doors
of the vast Temple of Jupiter on the Capitoline Hill.
And the Aqua Claudia and Aqua Anio Novus, the two greatest aqueducts of the imperial
city, cost 350,000,000 sestertii to complete.
Even these were dwarfed by the Forum of Trajan, whose cost may have approached a billion sestertii.
It is impossible to convert Roman sestertii to a modern currency with any accuracy.
But if we assume, on the basis of comparative prices, that an early imperial sestertius
had the purchasing power of about twenty dollars, the Colosseum cost the ancient equivalent
of $2,000,000,000 – about as much, in other words, as a very expensive modern stadium.
Now it’s time to tackle our second question: how much would it cost to build an exact replica
of the Colosseum?
Initially, I thought about trying to estimate the cost of doing everything – from quarrying
the stones to laying the concrete – the same way it was done 19 centuries ago.
This, however, proved impossible, since most ancient tools and techniques no longer exist.
Speaking only of transport, for example, you’d need to build hundreds of heavy wooden carts,
purchase and maintain a herd of oxen to draw them, and train a battalion of ox-drivers.
And if the work were done entirely by artisans using hand tools – many of whom would have
to be specially trained – the cost of labor alone would be astronomical.
So I decided instead to estimate the cost of building a replica of the Colosseum made
with the original materials but using modern machines and construction methods.
The site, I decided, would be in America, on a plot of land already owned by the builder,
and in an area with easy access to both a large labor pool and the raw materials.
I did not specify the region in which the replica would be built, or whether construction
would be done by unionized workers.
Then I tried to find an expert who could help me.
I emailed several classicists, a half-dozen professors of civil engineering, the International
Union of Bricklayers and Allied Craftworkers, and a limestone quarry in Indiana, among many
others.
Nobody responded.
Finally, I put up a community post here on YouTube, asking anyone with experience estimating
the costs of large masonry structures to send me a message.
To my profound relief, several subscribers heroically volunteered to undertake the task.
The first of the three detailed estimates I received was submitted by a subscriber with
the username Magnificus, an architectural project manager.
With the use of Computer Aided Design and estimating software, he proceeded level by
level, expensing by material and finishes.
Thus he assessed the cost of the senatorial podium, with its lavish use of marble, at
nearly $27,000,000, but assigned the uppermost tier of seating – with its wooden benches
– a cost of only $3,500,000.
He believed that the 160 marble statues perched in the upper arcades could be made for a cool
$4,000,000 with CNC stone carving machines.
The entire Colosseum, he estimated, could be replicated for as little as $150,000,000.
This, he acknowledged, seemed low, but he pointed out that the Colosseum had no modern
amenities, was made from materials that could be easily sourced, and was decorated in a
relatively straightforward and repetitive manner.
The next estimate was submitted by Tim Wilkinson, an engineer.
In his experience, reinforced concrete for a high-rise structure costs about $1,500 per
cubic yard.
Applying this metric to the Colosseum would give a figure of $450,000,000 for the foundations
alone, though Tim thinks that the actual expense would be much lower, thanks to economies of
scale.
Still, when factoring in the huge quantities of material needed for the seating bowl and
circuit wall, he believes that the total cost of a replica built with the best modern materials
would exceed a billion dollars.
The last and most detailed estimate was submitted by Jim Williams, a retired architect with
a background in engineering.
Jim estimated total material costs of about $400,000,000, including $250,000,000 of travertine
and $100,000,000 of marble.
The equipment required – 20 bulldozers, 10 concrete pumps, and a total of 30 cranes
– would cost about $25,000,000.
About 1100 workers would be needed, including 75 skilled stone carvers and 40 fresco artists.
Assuming a two-year construction time, labor costs would be just under $450,000,000.
Once construction management costs, permit fees, and all other expenses were accounted
for, the total price tag would be just under a billion dollars.
Since I lack the expertise to assess these estimates in any meaningful way, I’m most
intrigued by the differences between them, which reflect the fact that there is no single
answer to the question of how much it would cost to build a replica of the Colosseum.
The only way to answer the question would be to actually build a replica – and even
then, you’d only have one possible answer, contingent on a unique set of local circumstances.
In the first part of this video, I estimated that the original Colosseum cost something
like 100,000,000 sestertii, which I equated – more or less arbitrarily – with $2,000,000,000.
If, as it seems, the cost of producing a modern replica would be half that figure, or even
less, the difference is a testimony to modern construction technology, whose efficiencies
counterbalance the vastly higher costs of modern labor.
I won’t pretend that the figures thrown around in this video have any real validity.
These are estimates piled on assumptions, the turrets and battlements of a castle in
the air.
But the exercise is intriguing in itself, and hopefully illuminates something about
the ways and means of building an ancient wonder.
If you enjoyed this video, please consider supporting toldinstone on Patreon.
You might also enjoy my book, Naked Statues, Fat Gladiators, and War Elephants.
A special thanks to Magnificus, Tim Wilkinson, and Jim Williams; and thanks to all of you
for watching.