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15:20
Transcript
0:01
How much, in modern dollars, did the Colosseum
cost to build?
0:06
And how much would it cost to build an exact
replica today?
0:10
We’ll start with the first question.
0:14
The Romans reckoned costs in sestertii, big
brass coins worth a quarter of a denarius.
0:21
At the time the Colosseum was built, one sestertius
could buy two loaves of bread, four cups of
0:26
cheap wine, or a single cup of good wine.
0:30
A tunic cost about 15 sestertii, and the rent
for a decent apartment was probably between
0:36
300-500 sestertii a year.
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0:40
The average annual wage for an unskilled laborer
was around 1,000 sestertii.
0:46
A marble mausoleum along the Via Appia could
easily cost 10-20,000 sestertii.
0:51
A wealthy senator could spend 300,000 adding
a private bath to his house.
0:58
Simply finishing Nero’s Golden House cost
50,000,000 sestertii.
1:03
How did the Colosseum compare?
1:06
Since no literary source or inscription provides
any clues, we have to estimate on the basis
1:11
of labor and material costs.
1:14
The first task of the Colosseum’s builders
was to excavate the foundation trench, as
1:19
large as the building’s footprint and more
than 8 meters deep.
1:23
Removing something like 170,000 cubic meters
of earth and stone was an enormous task, involving
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1:30
thousands of workers.
1:32
Contrary to what you might assume, few of
them were slaves: although the private contractors
1:37
who built the Colosseum had small permanent
staffs of skilled slaves and freedmen, most
1:42
of the work was done by unskilled day laborers.
1:47
Following an approach pioneered by Janet DeLaine,
a professor of Roman archaeology at Oxford,
1:52
I used a nineteenth-century construction manual
to estimate the labor required to clear the
1:57
Colosseum’s foundation trench with hand
tools.
2:01
If I did the math right, something like 70,000
man-days of labor would have been required
2:07
to excavate and haul away 170,000 cubic meters
of rocky soil – but this does not account
2:12
for the fact that the workmen had to cut into
bedrock on the north side of the foundation
2:16
trench, and had to contend with a high water
table throughout.
2:21
So let’s say, conservatively, that 125,000
man-days of labor were required.
2:27
I’ll assume that the workmen earned an average
of 4 sestertii a day, which seems to have
2:32
been the going rate for a laborer in first-century
Rome.
2:36
By that reckoning, the cost of clearing the
Colosseum’s foundation trench was in the
2:40
neighborhood of 500,000 sestertii.
2:43
Next, the foundations were laid.
2:46
Like the building above it, the Colosseum’s
foundation was a huge ellipse about 60 meters
2:51
wide.
2:52
It consisted of two parts: a lower foundation
of solid concrete 7 meters thick, and a 6
2:59
meter thick upper foundation, also concrete,
honeycombed with service passages.
3:06
Roman concrete, as I’ve discussed in some
of my other videos, was not poured like modern
3:11
concrete, but spread in courses.
3:14
First, retaining walls of brick or stone were
constructed as a sort of form.
3:20
A layer of coarse aggregate – in the Colosseum’s
case, chunks of basalt and tufa – was laid
3:26
down between these walls, and pozzolana mortar
was troweled over the rubble bed, almost dry.
3:33
The mixture was then pounded firm with wooden
mallets.
3:37
Besides its strength and durability, Roman
concrete had the great virtue of being cheap.
3:43
All the materials were available locally;
and – unlike masonry – a large concrete
3:48
structure could be built largely with unskilled
labor.
3:52
By my best estimate, the upper and lower foundations
together used roughly 250,000 cubic meters
3:59
of rubble and concrete.
4:01
Again following Janet DeLaine, who wrote an
article on the relative costs of different
4:06
types of Roman construction, I estimate that
each cubic meter of concrete cost the equivalent
4:11
of 10 days’ wages for a laborer.
4:14
By our equation, that gives a total of about
10,000,000 sestertii for the foundation.
4:20
Next, work began on the superstructure.
4:24
Although most large Roman buildings were made
of brick-faced concrete, both the perimeter
4:28
wall and the interior support columns of the
Colosseum were built with massive blocks of
4:33
travertine, quarried at Tivoli and ferried
to Rome by barge.
4:37
The Colosseum required about 100,000 cubic
meters of travertine – roughly one-fiftieth,
4:42
incidentally, of all the travertine ever quarried
by the Romans.
4:47
The stone, cut into blocks with an average
weight of four tons, was lifted into place
4:52
by simple treadwheel cranes like the one pictured
in this relief, and clamped with 300 tons
4:57
of iron.
5:00
Travertine is a hard and heavy stone, difficult
to work and transport.
5:04
It was correspondingly expensive.
5:07
Each cubic meter, by DeLaine’s estimate,
cost the equivalent of 100 days’ wages for
5:12
a laborer.
5:14
The basic cost would have been amplified by
the fact that each block had to be lifted,
5:18
sometimes as much as 50 meters, by muscle
power.
5:22
Iron was also much more expensive than it
is now.
5:25
So let’s say that building the travertine
components of the Colosseum cost 50,000,000
5:31
sestertii.
5:32
Although the key structural elements of the
Colosseum were travertine, the vaults and
5:36
substructures under the seats used roughly
100,000 cubic meters of tufa and concrete.
5:43
Tufa – a soft volcanic stone – was considerably
less expensive than travertine, and concrete,
5:49
as we’ve seen, was cheaper still.
5:51
The relative economy of the materials, however,
was partially offset by the complexity of
5:56
constructing so many vaults, ramps, and passageways.
6:01
So I think that 20,000,000 sestertii is a
reasonable guess for the cost of the substructures
6:06
and passageways.
6:09
Except for the uppermost tier, which had wooden
benches, the seats of the Colosseum were made
6:14
of Carrara marble.
6:16
Although this was one of the least expensive
varieties of marble, it still cost far more
6:20
than travertine, perhaps the equivalent of
150 laborer-days per cubic meter.
6:26
I’ve never seen any estimate for the amount
of marble used in the Colosseum.
6:31
The lowest tier of seats, the Senatorial podium,
was built entirely of marble; the seats above
6:37
had brick substructures faced with marble
slabs.
6:41
On that basis, I’ll say, more or less arbitrarily,
that 5,000 cubic meters of marble were used
6:47
throughout the building.
6:49
If that number is anything like correct, the
cost of the marble would have been around
6:53
3,000,000 sestertii.
6:55
The corridors of the Colosseum were plastered,
painted, and equipped with lead pipes for
7:00
water fountains.
7:01
More than 150 life-size statues stood in the
arches of the upper stories, and imposing
7:07
quadriga groups crowned the main entrances.
7:11
The statues alone, to judge from attested
prices, would have collectively cost well
7:15
over a million sestertii.
7:18
Without attempting to estimate the expense
of each component, I think it’s reasonable
7:22
to suggest total finishing costs in the neighborhood
of 2,500,000 sestertii.
7:27
So: how much did it cost to build the Colosseum
19 centuries ago?
7:32
Adding up the estimates I’ve given to this
point brings us to 86,000,000 sestertii.
7:37
This, I suspect, is still too low, since basic
estimates on the basis of material fail to
7:43
account for the many challenges of constructing
a building on the Colosseum’s scale.
7:48
So let’s say, just to have a nice round
figure we can work with, that construction
7:52
cost something on the order of 100,000,000
sestertii.
7:57
This was a lot of money.
7:59
The average annual income for a Roman laborer
was around 1,000 sestertii.
8:04
Imperial Roman senators, who were required
to own property worth at least 1,000,000 sestertii,
8:09
were very wealthy men.
8:11
The two richest Romans known to us were worth
400,000,000 sestertii – four times the estimated
8:16
cost of the Colosseum.
8:19
But if my estimate is anything like correct,
the Colosseum was far from the most expensive
8:24
building project in Rome.
8:26
Domitian reportedly spent nearly 300 million
sestertii just gilding the roof and doors
8:31
of the vast Temple of Jupiter on the Capitoline
Hill.
8:35
And the Aqua Claudia and Aqua Anio Novus,
the two greatest aqueducts of the imperial
8:40
city, cost 350,000,000 sestertii to complete.
8:44
Even these were dwarfed by the Forum of Trajan,
whose cost may have approached a billion sestertii.
8:49
It is impossible to convert Roman sestertii
to a modern currency with any accuracy.
8:55
But if we assume, on the basis of comparative
prices, that an early imperial sestertius
9:01
had the purchasing power of about twenty dollars,
the Colosseum cost the ancient equivalent
9:05
of $2,000,000,000 – about as much, in other
words, as a very expensive modern stadium.
9:12
Now it’s time to tackle our second question:
how much would it cost to build an exact replica
9:17
of the Colosseum?
9:18
Initially, I thought about trying to estimate
the cost of doing everything – from quarrying
9:25
the stones to laying the concrete – the
same way it was done 19 centuries ago.
9:30
This, however, proved impossible, since most
ancient tools and techniques no longer exist.
9:37
Speaking only of transport, for example, you’d
need to build hundreds of heavy wooden carts,
9:43
purchase and maintain a herd of oxen to draw
them, and train a battalion of ox-drivers.
9:50
And if the work were done entirely by artisans
using hand tools – many of whom would have
9:54
to be specially trained – the cost of labor
alone would be astronomical.
9:59
So I decided instead to estimate the cost
of building a replica of the Colosseum made
10:05
with the original materials but using modern
machines and construction methods.
10:10
The site, I decided, would be in America,
on a plot of land already owned by the builder,
10:16
and in an area with easy access to both a
large labor pool and the raw materials.
10:22
I did not specify the region in which the
replica would be built, or whether construction
10:26
would be done by unionized workers.
10:30
Then I tried to find an expert who could help
me.
10:33
I emailed several classicists, a half-dozen
professors of civil engineering, the International
10:39
Union of Bricklayers and Allied Craftworkers,
and a limestone quarry in Indiana, among many
10:45
others.
10:46
Nobody responded.
10:48
Finally, I put up a community post here on
YouTube, asking anyone with experience estimating
10:55
the costs of large masonry structures to send
me a message.
10:59
To my profound relief, several subscribers
heroically volunteered to undertake the task.
11:05
The first of the three detailed estimates
I received was submitted by a subscriber with
11:10
the username Magnificus, an architectural
project manager.
11:15
With the use of Computer Aided Design and
estimating software, he proceeded level by
11:20
level, expensing by material and finishes.
11:23
Thus he assessed the cost of the senatorial
podium, with its lavish use of marble, at
11:29
nearly $27,000,000, but assigned the uppermost
tier of seating – with its wooden benches
11:34
– a cost of only $3,500,000.
11:37
He believed that the 160 marble statues perched
in the upper arcades could be made for a cool
11:44
$4,000,000 with CNC stone carving machines.
11:48
The entire Colosseum, he estimated, could
be replicated for as little as $150,000,000.
11:54
This, he acknowledged, seemed low, but he
pointed out that the Colosseum had no modern
12:00
amenities, was made from materials that could
be easily sourced, and was decorated in a
12:05
relatively straightforward and repetitive
manner.
12:09
The next estimate was submitted by Tim Wilkinson,
an engineer.
12:13
In his experience, reinforced concrete for
a high-rise structure costs about $1,500 per
12:19
cubic yard.
12:20
Applying this metric to the Colosseum would
give a figure of $450,000,000 for the foundations
12:25
alone, though Tim thinks that the actual expense
would be much lower, thanks to economies of
12:29
scale.
12:31
Still, when factoring in the huge quantities
of material needed for the seating bowl and
12:35
circuit wall, he believes that the total cost
of a replica built with the best modern materials
12:41
would exceed a billion dollars.
12:44
The last and most detailed estimate was submitted
by Jim Williams, a retired architect with
12:50
a background in engineering.
12:52
Jim estimated total material costs of about
$400,000,000, including $250,000,000 of travertine
12:59
and $100,000,000 of marble.
13:02
The equipment required – 20 bulldozers,
10 concrete pumps, and a total of 30 cranes
13:08
– would cost about $25,000,000.
13:12
About 1100 workers would be needed, including
75 skilled stone carvers and 40 fresco artists.
13:20
Assuming a two-year construction time, labor
costs would be just under $450,000,000.
13:25
Once construction management costs, permit
fees, and all other expenses were accounted
13:30
for, the total price tag would be just under
a billion dollars.
13:35
Since I lack the expertise to assess these
estimates in any meaningful way, I’m most
13:39
intrigued by the differences between them,
which reflect the fact that there is no single
13:44
answer to the question of how much it would
cost to build a replica of the Colosseum.
13:49
The only way to answer the question would
be to actually build a replica – and even
13:53
then, you’d only have one possible answer,
contingent on a unique set of local circumstances.
13:59
In the first part of this video, I estimated
that the original Colosseum cost something
14:05
like 100,000,000 sestertii, which I equated
– more or less arbitrarily – with $2,000,000,000.
14:11
If, as it seems, the cost of producing a modern
replica would be half that figure, or even
14:18
less, the difference is a testimony to modern
construction technology, whose efficiencies
14:23
counterbalance the vastly higher costs of
modern labor.
14:28
I won’t pretend that the figures thrown
around in this video have any real validity.
14:33
These are estimates piled on assumptions,
the turrets and battlements of a castle in
14:38
the air.
14:40
But the exercise is intriguing in itself,
and hopefully illuminates something about
14:44
the ways and means of building an ancient
wonder.
14:49
If you enjoyed this video, please consider
supporting toldinstone on Patreon.
14:54
You might also enjoy my book, Naked Statues,
Fat Gladiators, and War Elephants.
15:00
A special thanks to Magnificus, Tim Wilkinson,
and Jim Williams; and thanks to all of you
15:06
for watching.
— end of transcript —
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