WEBVTT 00:00:01.690 --> 00:00:06.759 How much, in modern dollars, did the Colosseum cost to build? 00:00:06.759 --> 00:00:10.730 And how much would it cost to build an exact replica today? 00:00:10.730 --> 00:00:14.500 We’ll start with the first question. 00:00:14.500 --> 00:00:21.259 The Romans reckoned costs in sestertii, big brass coins worth a quarter of a denarius. 00:00:21.260 --> 00:00:26.840 At the time the Colosseum was built, one sestertius could buy two loaves of bread, four cups of 00:00:26.839 --> 00:00:30.719 cheap wine, or a single cup of good wine. 00:00:30.719 --> 00:00:36.488 A tunic cost about 15 sestertii, and the rent for a decent apartment was probably between 00:00:36.488 --> 00:00:40.599 300-500 sestertii a year. 00:00:40.600 --> 00:00:46.189 The average annual wage for an unskilled laborer was around 1,000 sestertii. 00:00:46.189 --> 00:00:51.119 A marble mausoleum along the Via Appia could easily cost 10-20,000 sestertii. 00:00:51.119 --> 00:00:58.408 A wealthy senator could spend 300,000 adding a private bath to his house. 00:00:58.408 --> 00:01:03.728 Simply finishing Nero’s Golden House cost 50,000,000 sestertii. 00:01:03.728 --> 00:01:06.500 How did the Colosseum compare? 00:01:06.500 --> 00:01:11.549 Since no literary source or inscription provides any clues, we have to estimate on the basis 00:01:11.549 --> 00:01:14.759 of labor and material costs. 00:01:14.760 --> 00:01:19.570 The first task of the Colosseum’s builders was to excavate the foundation trench, as 00:01:19.569 --> 00:01:23.429 large as the building’s footprint and more than 8 meters deep. 00:01:23.430 --> 00:01:30.340 Removing something like 170,000 cubic meters of earth and stone was an enormous task, involving 00:01:30.340 --> 00:01:32.700 thousands of workers. 00:01:32.700 --> 00:01:37.439 Contrary to what you might assume, few of them were slaves: although the private contractors 00:01:37.439 --> 00:01:42.609 who built the Colosseum had small permanent staffs of skilled slaves and freedmen, most 00:01:42.609 --> 00:01:47.019 of the work was done by unskilled day laborers. 00:01:47.019 --> 00:01:52.689 Following an approach pioneered by Janet DeLaine, a professor of Roman archaeology at Oxford, 00:01:52.689 --> 00:01:57.599 I used a nineteenth-century construction manual to estimate the labor required to clear the 00:01:57.599 --> 00:02:01.109 Colosseum’s foundation trench with hand tools. 00:02:01.109 --> 00:02:07.079 If I did the math right, something like 70,000 man-days of labor would have been required 00:02:07.079 --> 00:02:12.669 to excavate and haul away 170,000 cubic meters of rocky soil – but this does not account 00:02:12.669 --> 00:02:16.691 for the fact that the workmen had to cut into bedrock on the north side of the foundation 00:02:16.692 --> 00:02:21.189 trench, and had to contend with a high water table throughout. 00:02:21.189 --> 00:02:27.139 So let’s say, conservatively, that 125,000 man-days of labor were required. 00:02:27.139 --> 00:02:32.419 I’ll assume that the workmen earned an average of 4 sestertii a day, which seems to have 00:02:32.419 --> 00:02:36.299 been the going rate for a laborer in first-century Rome. 00:02:36.300 --> 00:02:40.230 By that reckoning, the cost of clearing the Colosseum’s foundation trench was in the 00:02:40.229 --> 00:02:43.609 neighborhood of 500,000 sestertii. 00:02:43.610 --> 00:02:46.990 Next, the foundations were laid. 00:02:46.990 --> 00:02:51.650 Like the building above it, the Colosseum’s foundation was a huge ellipse about 60 meters 00:02:51.650 --> 00:02:52.890 wide. 00:02:52.889 --> 00:02:59.250 It consisted of two parts: a lower foundation of solid concrete 7 meters thick, and a 6 00:02:59.250 --> 00:03:06.050 meter thick upper foundation, also concrete, honeycombed with service passages. 00:03:06.050 --> 00:03:11.380 Roman concrete, as I’ve discussed in some of my other videos, was not poured like modern 00:03:11.379 --> 00:03:14.209 concrete, but spread in courses. 00:03:14.209 --> 00:03:20.550 First, retaining walls of brick or stone were constructed as a sort of form. 00:03:20.550 --> 00:03:26.150 A layer of coarse aggregate – in the Colosseum’s case, chunks of basalt and tufa – was laid 00:03:26.150 --> 00:03:33.310 down between these walls, and pozzolana mortar was troweled over the rubble bed, almost dry. 00:03:33.310 --> 00:03:37.620 The mixture was then pounded firm with wooden mallets. 00:03:37.620 --> 00:03:43.640 Besides its strength and durability, Roman concrete had the great virtue of being cheap. 00:03:43.639 --> 00:03:48.529 All the materials were available locally; and – unlike masonry – a large concrete 00:03:48.530 --> 00:03:52.949 structure could be built largely with unskilled labor. 00:03:52.949 --> 00:03:59.089 By my best estimate, the upper and lower foundations together used roughly 250,000 cubic meters 00:03:59.090 --> 00:04:01.489 of rubble and concrete. 00:04:01.489 --> 00:04:06.110 Again following Janet DeLaine, who wrote an article on the relative costs of different 00:04:06.110 --> 00:04:11.360 types of Roman construction, I estimate that each cubic meter of concrete cost the equivalent 00:04:11.360 --> 00:04:14.340 of 10 days’ wages for a laborer. 00:04:14.340 --> 00:04:20.220 By our equation, that gives a total of about 10,000,000 sestertii for the foundation. 00:04:20.220 --> 00:04:24.050 Next, work began on the superstructure. 00:04:24.050 --> 00:04:28.520 Although most large Roman buildings were made of brick-faced concrete, both the perimeter 00:04:28.519 --> 00:04:33.069 wall and the interior support columns of the Colosseum were built with massive blocks of 00:04:33.069 --> 00:04:37.939 travertine, quarried at Tivoli and ferried to Rome by barge. 00:04:37.939 --> 00:04:42.379 The Colosseum required about 100,000 cubic meters of travertine – roughly one-fiftieth, 00:04:42.379 --> 00:04:47.649 incidentally, of all the travertine ever quarried by the Romans. 00:04:47.649 --> 00:04:52.679 The stone, cut into blocks with an average weight of four tons, was lifted into place 00:04:52.680 --> 00:04:57.810 by simple treadwheel cranes like the one pictured in this relief, and clamped with 300 tons 00:04:57.810 --> 00:05:00.199 of iron. 00:05:00.199 --> 00:05:04.830 Travertine is a hard and heavy stone, difficult to work and transport. 00:05:04.829 --> 00:05:07.959 It was correspondingly expensive. 00:05:07.959 --> 00:05:12.750 Each cubic meter, by DeLaine’s estimate, cost the equivalent of 100 days’ wages for 00:05:12.750 --> 00:05:14.370 a laborer. 00:05:14.370 --> 00:05:18.530 The basic cost would have been amplified by the fact that each block had to be lifted, 00:05:18.529 --> 00:05:22.549 sometimes as much as 50 meters, by muscle power. 00:05:22.550 --> 00:05:25.699 Iron was also much more expensive than it is now. 00:05:25.699 --> 00:05:31.129 So let’s say that building the travertine components of the Colosseum cost 50,000,000 00:05:31.129 --> 00:05:32.509 sestertii. 00:05:32.509 --> 00:05:36.370 Although the key structural elements of the Colosseum were travertine, the vaults and 00:05:36.370 --> 00:05:43.180 substructures under the seats used roughly 100,000 cubic meters of tufa and concrete. 00:05:43.180 --> 00:05:49.040 Tufa – a soft volcanic stone – was considerably less expensive than travertine, and concrete, 00:05:49.040 --> 00:05:51.540 as we’ve seen, was cheaper still. 00:05:51.540 --> 00:05:56.919 The relative economy of the materials, however, was partially offset by the complexity of 00:05:56.918 --> 00:06:01.529 constructing so many vaults, ramps, and passageways. 00:06:01.529 --> 00:06:06.899 So I think that 20,000,000 sestertii is a reasonable guess for the cost of the substructures 00:06:06.899 --> 00:06:09.339 and passageways. 00:06:09.339 --> 00:06:14.388 Except for the uppermost tier, which had wooden benches, the seats of the Colosseum were made 00:06:14.389 --> 00:06:16.120 of Carrara marble. 00:06:16.120 --> 00:06:20.478 Although this was one of the least expensive varieties of marble, it still cost far more 00:06:20.478 --> 00:06:26.180 than travertine, perhaps the equivalent of 150 laborer-days per cubic meter. 00:06:26.180 --> 00:06:31.410 I’ve never seen any estimate for the amount of marble used in the Colosseum. 00:06:31.410 --> 00:06:37.229 The lowest tier of seats, the Senatorial podium, was built entirely of marble; the seats above 00:06:37.228 --> 00:06:41.199 had brick substructures faced with marble slabs. 00:06:41.199 --> 00:06:47.569 On that basis, I’ll say, more or less arbitrarily, that 5,000 cubic meters of marble were used 00:06:47.569 --> 00:06:49.480 throughout the building. 00:06:49.480 --> 00:06:53.560 If that number is anything like correct, the cost of the marble would have been around 00:06:53.560 --> 00:06:55.788 3,000,000 sestertii. 00:06:55.788 --> 00:07:00.459 The corridors of the Colosseum were plastered, painted, and equipped with lead pipes for 00:07:00.459 --> 00:07:01.788 water fountains. 00:07:01.788 --> 00:07:07.469 More than 150 life-size statues stood in the arches of the upper stories, and imposing 00:07:07.470 --> 00:07:11.050 quadriga groups crowned the main entrances. 00:07:11.050 --> 00:07:15.670 The statues alone, to judge from attested prices, would have collectively cost well 00:07:15.670 --> 00:07:18.050 over a million sestertii. 00:07:18.050 --> 00:07:22.310 Without attempting to estimate the expense of each component, I think it’s reasonable 00:07:22.310 --> 00:07:27.819 to suggest total finishing costs in the neighborhood of 2,500,000 sestertii. 00:07:27.819 --> 00:07:32.430 So: how much did it cost to build the Colosseum 19 centuries ago? 00:07:32.430 --> 00:07:37.168 Adding up the estimates I’ve given to this point brings us to 86,000,000 sestertii. 00:07:37.168 --> 00:07:43.359 This, I suspect, is still too low, since basic estimates on the basis of material fail to 00:07:43.360 --> 00:07:48.610 account for the many challenges of constructing a building on the Colosseum’s scale. 00:07:48.610 --> 00:07:52.639 So let’s say, just to have a nice round figure we can work with, that construction 00:07:52.639 --> 00:07:57.410 cost something on the order of 100,000,000 sestertii. 00:07:57.410 --> 00:07:59.210 This was a lot of money. 00:07:59.209 --> 00:08:04.649 The average annual income for a Roman laborer was around 1,000 sestertii. 00:08:04.649 --> 00:08:09.519 Imperial Roman senators, who were required to own property worth at least 1,000,000 sestertii, 00:08:09.519 --> 00:08:11.740 were very wealthy men. 00:08:11.740 --> 00:08:16.960 The two richest Romans known to us were worth 400,000,000 sestertii – four times the estimated 00:08:16.959 --> 00:08:19.629 cost of the Colosseum. 00:08:19.629 --> 00:08:24.519 But if my estimate is anything like correct, the Colosseum was far from the most expensive 00:08:24.519 --> 00:08:26.740 building project in Rome. 00:08:26.740 --> 00:08:31.519 Domitian reportedly spent nearly 300 million sestertii just gilding the roof and doors 00:08:31.519 --> 00:08:35.210 of the vast Temple of Jupiter on the Capitoline Hill. 00:08:35.210 --> 00:08:40.060 And the Aqua Claudia and Aqua Anio Novus, the two greatest aqueducts of the imperial 00:08:40.059 --> 00:08:44.439 city, cost 350,000,000 sestertii to complete. 00:08:44.440 --> 00:08:49.529 Even these were dwarfed by the Forum of Trajan, whose cost may have approached a billion sestertii. 00:08:49.528 --> 00:08:55.509 It is impossible to convert Roman sestertii to a modern currency with any accuracy. 00:08:55.509 --> 00:09:01.350 But if we assume, on the basis of comparative prices, that an early imperial sestertius 00:09:01.350 --> 00:09:05.490 had the purchasing power of about twenty dollars, the Colosseum cost the ancient equivalent 00:09:05.490 --> 00:09:12.470 of $2,000,000,000 – about as much, in other words, as a very expensive modern stadium. 00:09:12.470 --> 00:09:17.750 Now it’s time to tackle our second question: how much would it cost to build an exact replica 00:09:17.750 --> 00:09:18.958 of the Colosseum? 00:09:18.958 --> 00:09:25.119 Initially, I thought about trying to estimate the cost of doing everything – from quarrying 00:09:25.120 --> 00:09:30.629 the stones to laying the concrete – the same way it was done 19 centuries ago. 00:09:30.629 --> 00:09:37.740 This, however, proved impossible, since most ancient tools and techniques no longer exist. 00:09:37.740 --> 00:09:43.549 Speaking only of transport, for example, you’d need to build hundreds of heavy wooden carts, 00:09:43.549 --> 00:09:50.139 purchase and maintain a herd of oxen to draw them, and train a battalion of ox-drivers. 00:09:50.139 --> 00:09:54.720 And if the work were done entirely by artisans using hand tools – many of whom would have 00:09:54.720 --> 00:09:59.940 to be specially trained – the cost of labor alone would be astronomical. 00:09:59.940 --> 00:10:05.130 So I decided instead to estimate the cost of building a replica of the Colosseum made 00:10:05.129 --> 00:10:10.019 with the original materials but using modern machines and construction methods. 00:10:10.019 --> 00:10:16.539 The site, I decided, would be in America, on a plot of land already owned by the builder, 00:10:16.539 --> 00:10:22.569 and in an area with easy access to both a large labor pool and the raw materials. 00:10:22.570 --> 00:10:26.820 I did not specify the region in which the replica would be built, or whether construction 00:10:26.820 --> 00:10:30.320 would be done by unionized workers. 00:10:30.320 --> 00:10:33.000 Then I tried to find an expert who could help me. 00:10:33.000 --> 00:10:39.330 I emailed several classicists, a half-dozen professors of civil engineering, the International 00:10:39.330 --> 00:10:45.330 Union of Bricklayers and Allied Craftworkers, and a limestone quarry in Indiana, among many 00:10:45.330 --> 00:10:46.330 others. 00:10:46.330 --> 00:10:48.000 Nobody responded. 00:10:48.000 --> 00:10:55.049 Finally, I put up a community post here on YouTube, asking anyone with experience estimating 00:10:55.049 --> 00:10:59.088 the costs of large masonry structures to send me a message. 00:10:59.089 --> 00:11:05.870 To my profound relief, several subscribers heroically volunteered to undertake the task. 00:11:05.870 --> 00:11:10.289 The first of the three detailed estimates I received was submitted by a subscriber with 00:11:10.289 --> 00:11:15.028 the username Magnificus, an architectural project manager. 00:11:15.028 --> 00:11:20.088 With the use of Computer Aided Design and estimating software, he proceeded level by 00:11:20.089 --> 00:11:23.430 level, expensing by material and finishes. 00:11:23.429 --> 00:11:29.469 Thus he assessed the cost of the senatorial podium, with its lavish use of marble, at 00:11:29.470 --> 00:11:34.430 nearly $27,000,000, but assigned the uppermost tier of seating – with its wooden benches 00:11:34.429 --> 00:11:37.829 – a cost of only $3,500,000. 00:11:37.830 --> 00:11:44.120 He believed that the 160 marble statues perched in the upper arcades could be made for a cool 00:11:44.120 --> 00:11:48.750 $4,000,000 with CNC stone carving machines. 00:11:48.750 --> 00:11:54.919 The entire Colosseum, he estimated, could be replicated for as little as $150,000,000. 00:11:54.919 --> 00:12:00.669 This, he acknowledged, seemed low, but he pointed out that the Colosseum had no modern 00:12:00.669 --> 00:12:05.319 amenities, was made from materials that could be easily sourced, and was decorated in a 00:12:05.320 --> 00:12:09.019 relatively straightforward and repetitive manner. 00:12:09.019 --> 00:12:13.509 The next estimate was submitted by Tim Wilkinson, an engineer. 00:12:13.509 --> 00:12:19.429 In his experience, reinforced concrete for a high-rise structure costs about $1,500 per 00:12:19.429 --> 00:12:20.649 cubic yard. 00:12:20.649 --> 00:12:25.809 Applying this metric to the Colosseum would give a figure of $450,000,000 for the foundations 00:12:25.809 --> 00:12:29.969 alone, though Tim thinks that the actual expense would be much lower, thanks to economies of 00:12:29.970 --> 00:12:31.000 scale. 00:12:31.000 --> 00:12:35.929 Still, when factoring in the huge quantities of material needed for the seating bowl and 00:12:35.929 --> 00:12:41.419 circuit wall, he believes that the total cost of a replica built with the best modern materials 00:12:41.419 --> 00:12:44.429 would exceed a billion dollars. 00:12:44.429 --> 00:12:50.229 The last and most detailed estimate was submitted by Jim Williams, a retired architect with 00:12:50.230 --> 00:12:52.379 a background in engineering. 00:12:52.379 --> 00:12:59.549 Jim estimated total material costs of about $400,000,000, including $250,000,000 of travertine 00:12:59.549 --> 00:13:02.870 and $100,000,000 of marble. 00:13:02.870 --> 00:13:08.959 The equipment required – 20 bulldozers, 10 concrete pumps, and a total of 30 cranes 00:13:08.958 --> 00:13:12.549 – would cost about $25,000,000. 00:13:12.549 --> 00:13:20.189 About 1100 workers would be needed, including 75 skilled stone carvers and 40 fresco artists. 00:13:20.190 --> 00:13:25.800 Assuming a two-year construction time, labor costs would be just under $450,000,000. 00:13:25.799 --> 00:13:30.669 Once construction management costs, permit fees, and all other expenses were accounted 00:13:30.669 --> 00:13:35.519 for, the total price tag would be just under a billion dollars. 00:13:35.519 --> 00:13:39.649 Since I lack the expertise to assess these estimates in any meaningful way, I’m most 00:13:39.649 --> 00:13:44.299 intrigued by the differences between them, which reflect the fact that there is no single 00:13:44.299 --> 00:13:49.799 answer to the question of how much it would cost to build a replica of the Colosseum. 00:13:49.799 --> 00:13:53.889 The only way to answer the question would be to actually build a replica – and even 00:13:53.889 --> 00:13:59.690 then, you’d only have one possible answer, contingent on a unique set of local circumstances. 00:13:59.690 --> 00:14:05.720 In the first part of this video, I estimated that the original Colosseum cost something 00:14:05.720 --> 00:14:11.399 like 100,000,000 sestertii, which I equated – more or less arbitrarily – with $2,000,000,000. 00:14:11.399 --> 00:14:18.350 If, as it seems, the cost of producing a modern replica would be half that figure, or even 00:14:18.350 --> 00:14:23.350 less, the difference is a testimony to modern construction technology, whose efficiencies 00:14:23.350 --> 00:14:28.019 counterbalance the vastly higher costs of modern labor. 00:14:28.019 --> 00:14:33.730 I won’t pretend that the figures thrown around in this video have any real validity. 00:14:33.730 --> 00:14:38.680 These are estimates piled on assumptions, the turrets and battlements of a castle in 00:14:38.679 --> 00:14:40.219 the air. 00:14:40.220 --> 00:14:44.710 But the exercise is intriguing in itself, and hopefully illuminates something about 00:14:44.710 --> 00:14:49.730 the ways and means of building an ancient wonder. 00:14:49.730 --> 00:14:54.589 If you enjoyed this video, please consider supporting toldinstone on Patreon. 00:14:54.589 --> 00:15:00.920 You might also enjoy my book, Naked Statues, Fat Gladiators, and War Elephants. 00:15:00.919 --> 00:15:06.528 A special thanks to Magnificus, Tim Wilkinson, and Jim Williams; and thanks to all of you 00:15:06.528 --> 00:15:07.200 for watching.