[00:01] How much, in modern dollars, did the Colosseum
cost to build?
[00:06] And how much would it cost to build an exact
replica today?
[00:10] We’ll start with the first question.
[00:14] The Romans reckoned costs in sestertii, big
brass coins worth a quarter of a denarius.
[00:21] At the time the Colosseum was built, one sestertius
could buy two loaves of bread, four cups of
[00:26] cheap wine, or a single cup of good wine.
[00:30] A tunic cost about 15 sestertii, and the rent
for a decent apartment was probably between
[00:36] 300-500 sestertii a year.
[00:40] The average annual wage for an unskilled laborer
was around 1,000 sestertii.
[00:46] A marble mausoleum along the Via Appia could
easily cost 10-20,000 sestertii.
[00:51] A wealthy senator could spend 300,000 adding
a private bath to his house.
[00:58] Simply finishing Nero’s Golden House cost
50,000,000 sestertii.
[01:03] How did the Colosseum compare?
[01:06] Since no literary source or inscription provides
any clues, we have to estimate on the basis
[01:11] of labor and material costs.
[01:14] The first task of the Colosseum’s builders
was to excavate the foundation trench, as
[01:19] large as the building’s footprint and more
than 8 meters deep.
[01:23] Removing something like 170,000 cubic meters
of earth and stone was an enormous task, involving
[01:30] thousands of workers.
[01:32] Contrary to what you might assume, few of
them were slaves: although the private contractors
[01:37] who built the Colosseum had small permanent
staffs of skilled slaves and freedmen, most
[01:42] of the work was done by unskilled day laborers.
[01:47] Following an approach pioneered by Janet DeLaine,
a professor of Roman archaeology at Oxford,
[01:52] I used a nineteenth-century construction manual
to estimate the labor required to clear the
[01:57] Colosseum’s foundation trench with hand
tools.
[02:01] If I did the math right, something like 70,000
man-days of labor would have been required
[02:07] to excavate and haul away 170,000 cubic meters
of rocky soil – but this does not account
[02:12] for the fact that the workmen had to cut into
bedrock on the north side of the foundation
[02:16] trench, and had to contend with a high water
table throughout.
[02:21] So let’s say, conservatively, that 125,000
man-days of labor were required.
[02:27] I’ll assume that the workmen earned an average
of 4 sestertii a day, which seems to have
[02:32] been the going rate for a laborer in first-century
Rome.
[02:36] By that reckoning, the cost of clearing the
Colosseum’s foundation trench was in the
[02:40] neighborhood of 500,000 sestertii.
[02:43] Next, the foundations were laid.
[02:46] Like the building above it, the Colosseum’s
foundation was a huge ellipse about 60 meters
[02:51] wide.
[02:52] It consisted of two parts: a lower foundation
of solid concrete 7 meters thick, and a 6
[02:59] meter thick upper foundation, also concrete,
honeycombed with service passages.
[03:06] Roman concrete, as I’ve discussed in some
of my other videos, was not poured like modern
[03:11] concrete, but spread in courses.
[03:14] First, retaining walls of brick or stone were
constructed as a sort of form.
[03:20] A layer of coarse aggregate – in the Colosseum’s
case, chunks of basalt and tufa – was laid
[03:26] down between these walls, and pozzolana mortar
was troweled over the rubble bed, almost dry.
[03:33] The mixture was then pounded firm with wooden
mallets.
[03:37] Besides its strength and durability, Roman
concrete had the great virtue of being cheap.
[03:43] All the materials were available locally;
and – unlike masonry – a large concrete
[03:48] structure could be built largely with unskilled
labor.
[03:52] By my best estimate, the upper and lower foundations
together used roughly 250,000 cubic meters
[03:59] of rubble and concrete.
[04:01] Again following Janet DeLaine, who wrote an
article on the relative costs of different
[04:06] types of Roman construction, I estimate that
each cubic meter of concrete cost the equivalent
[04:11] of 10 days’ wages for a laborer.
[04:14] By our equation, that gives a total of about
10,000,000 sestertii for the foundation.
[04:20] Next, work began on the superstructure.
[04:24] Although most large Roman buildings were made
of brick-faced concrete, both the perimeter
[04:28] wall and the interior support columns of the
Colosseum were built with massive blocks of
[04:33] travertine, quarried at Tivoli and ferried
to Rome by barge.
[04:37] The Colosseum required about 100,000 cubic
meters of travertine – roughly one-fiftieth,
[04:42] incidentally, of all the travertine ever quarried
by the Romans.
[04:47] The stone, cut into blocks with an average
weight of four tons, was lifted into place
[04:52] by simple treadwheel cranes like the one pictured
in this relief, and clamped with 300 tons
[04:57] of iron.
[05:00] Travertine is a hard and heavy stone, difficult
to work and transport.
[05:04] It was correspondingly expensive.
[05:07] Each cubic meter, by DeLaine’s estimate,
cost the equivalent of 100 days’ wages for
[05:12] a laborer.
[05:14] The basic cost would have been amplified by
the fact that each block had to be lifted,
[05:18] sometimes as much as 50 meters, by muscle
power.
[05:22] Iron was also much more expensive than it
is now.
[05:25] So let’s say that building the travertine
components of the Colosseum cost 50,000,000
[05:31] sestertii.
[05:32] Although the key structural elements of the
Colosseum were travertine, the vaults and
[05:36] substructures under the seats used roughly
100,000 cubic meters of tufa and concrete.
[05:43] Tufa – a soft volcanic stone – was considerably
less expensive than travertine, and concrete,
[05:49] as we’ve seen, was cheaper still.
[05:51] The relative economy of the materials, however,
was partially offset by the complexity of
[05:56] constructing so many vaults, ramps, and passageways.
[06:01] So I think that 20,000,000 sestertii is a
reasonable guess for the cost of the substructures
[06:06] and passageways.
[06:09] Except for the uppermost tier, which had wooden
benches, the seats of the Colosseum were made
[06:14] of Carrara marble.
[06:16] Although this was one of the least expensive
varieties of marble, it still cost far more
[06:20] than travertine, perhaps the equivalent of
150 laborer-days per cubic meter.
[06:26] I’ve never seen any estimate for the amount
of marble used in the Colosseum.
[06:31] The lowest tier of seats, the Senatorial podium,
was built entirely of marble; the seats above
[06:37] had brick substructures faced with marble
slabs.
[06:41] On that basis, I’ll say, more or less arbitrarily,
that 5,000 cubic meters of marble were used
[06:47] throughout the building.
[06:49] If that number is anything like correct, the
cost of the marble would have been around
[06:53] 3,000,000 sestertii.
[06:55] The corridors of the Colosseum were plastered,
painted, and equipped with lead pipes for
[07:00] water fountains.
[07:01] More than 150 life-size statues stood in the
arches of the upper stories, and imposing
[07:07] quadriga groups crowned the main entrances.
[07:11] The statues alone, to judge from attested
prices, would have collectively cost well
[07:15] over a million sestertii.
[07:18] Without attempting to estimate the expense
of each component, I think it’s reasonable
[07:22] to suggest total finishing costs in the neighborhood
of 2,500,000 sestertii.
[07:27] So: how much did it cost to build the Colosseum
19 centuries ago?
[07:32] Adding up the estimates I’ve given to this
point brings us to 86,000,000 sestertii.
[07:37] This, I suspect, is still too low, since basic
estimates on the basis of material fail to
[07:43] account for the many challenges of constructing
a building on the Colosseum’s scale.
[07:48] So let’s say, just to have a nice round
figure we can work with, that construction
[07:52] cost something on the order of 100,000,000
sestertii.
[07:57] This was a lot of money.
[07:59] The average annual income for a Roman laborer
was around 1,000 sestertii.
[08:04] Imperial Roman senators, who were required
to own property worth at least 1,000,000 sestertii,
[08:09] were very wealthy men.
[08:11] The two richest Romans known to us were worth
400,000,000 sestertii – four times the estimated
[08:16] cost of the Colosseum.
[08:19] But if my estimate is anything like correct,
the Colosseum was far from the most expensive
[08:24] building project in Rome.
[08:26] Domitian reportedly spent nearly 300 million
sestertii just gilding the roof and doors
[08:31] of the vast Temple of Jupiter on the Capitoline
Hill.
[08:35] And the Aqua Claudia and Aqua Anio Novus,
the two greatest aqueducts of the imperial
[08:40] city, cost 350,000,000 sestertii to complete.
[08:44] Even these were dwarfed by the Forum of Trajan,
whose cost may have approached a billion sestertii.
[08:49] It is impossible to convert Roman sestertii
to a modern currency with any accuracy.
[08:55] But if we assume, on the basis of comparative
prices, that an early imperial sestertius
[09:01] had the purchasing power of about twenty dollars,
the Colosseum cost the ancient equivalent
[09:05] of $2,000,000,000 – about as much, in other
words, as a very expensive modern stadium.
[09:12] Now it’s time to tackle our second question:
how much would it cost to build an exact replica
[09:17] of the Colosseum?
[09:18] Initially, I thought about trying to estimate
the cost of doing everything – from quarrying
[09:25] the stones to laying the concrete – the
same way it was done 19 centuries ago.
[09:30] This, however, proved impossible, since most
ancient tools and techniques no longer exist.
[09:37] Speaking only of transport, for example, you’d
need to build hundreds of heavy wooden carts,
[09:43] purchase and maintain a herd of oxen to draw
them, and train a battalion of ox-drivers.
[09:50] And if the work were done entirely by artisans
using hand tools – many of whom would have
[09:54] to be specially trained – the cost of labor
alone would be astronomical.
[09:59] 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.