Rome population denser than modern Manhattan?

Here's an interesting video that supports the theory that Augustan Rome had a greater population density than the modern Manhattan borough in New York City.

First, one needs to assume that the population at the time of Augustus was 800,000 to 1,200,000.

Using the layout of the city of Rome outlined in the Severan Map created in 203-11 AD (known as Forma Urbis Romae), one is able to calculate the area of Rome 24 km2

FRAGMENT OF THE FORMA URBIS ROMAE. DATE: A.D. 203–211. MATERIAL: Marble, DIMENSIONS: 26 inches by 23.6 inches. FOUND: Rome, Italy.

Using population calculated from records of grain and pork supplied to the city, the video proposes that the population density of Augustan Rome was greater than modern Manhattan. 

Augustan Rome: 41,500 persons / km2

Manhattan, NYC: 28,000 persons / km2

Hong Kong: 6,300 persons / km2 

Even if this is a gross exaggeration, Ancient Rome was incredible for its infrastructure planning and services. The video suggests how the population of Ancient Rome could be so dense:

Brief article on the Forma Urbis Romae:

Quote

The Forma Urbis Romae, or map of the city of Rome, was a massive plan of the layout of the city under the emperor Septimius Severus (r. A.D. 193–211). Although only a small portion of the plan survives, scholars are relatively certain it illustrated most of the city. This fragment shows commercial structures on the southeastern slope of the Viminal Hill. The Forma Urbis adorned the wall of a room in Rome’s Temple of Peace that might have served as an archive of maps and records.

https://www.archaeology.org/issues/337-1905/features/7547-maps-rome-forma-urbis-romae

I find this topic very interesting too. I tried to raise it before (see below), but noone seemed to be willing to participate in the discussion at that time.

I've seen quite a few publications on this subject, the lowest estimate I bumped into was 400,000 inhabitants of Rome in the 1st century AD. Rodney Stark gave the figure of 650,000 inhabitants. Andrey Movchan (financial professional, amateur historian) claimed 1.5 mln inhabitants. So the high variance of the estimates seems rather perplexing. 

My personal view is that multi-storey buildings capable of providing shelter to so many people were highly unlikely to be present in Rome of those early ages. I reckon, double-storied private houses was the maximum one could find. Perhaps there was the daily high turnover of visitors from other places, given Rome's special place as the leading center of trade and exchange of its time, this could boost Rome's total population to very high numbers at certain hours of day, but as far as permanent residents are concerned I find it hard to believe that the number could be that high and comparable with todays' Europe largest cities. This is not only about the difficulty of providing staples or utilities (like water, kindling or food) to support so many inhabitants. Cicero is known to have purchased his luxury house on the Palatine hill for 3.5 mln sestertii, and that was even before emperor Augustus introduced his entry requirements for Roman Senators to hold at least 1 mln  sestertii of wealth. So this all hints that the land in Rome was rather expensive to support the construction of affordable housing to shelter millions of inhabitants.

According to the below video, Rome's population never exceeded 0.4 mln in the 1st century CE (check out the very bottom row with numbers)

Serious historians specialized in Roman history estimate that Rome had around 1 million inhabitants. This estimate is based on two facts:

1. Augustus claimed that 300,000 to 200,000 Roman citizens received free grain, given adult males were 28% of the population in ancient societies this implies that Rome's citizen population was close to 1 million, adding slaves and metics and you get to over 1 million.

2. The area enclosed by the 14-regions of Rome delimited by Augustus was1783 hectares, a statistical analysis on the number of apartments that archeologists have identified in Roman cities suggest that Rome's population density might have been around 500 to 550 per hectare, which yields a population around 900,000 to 1,000,000 for the Rome of Augustus. See Hanson and Ortman (2017): https://www.researchgate.net/publication/321077578_A_systematic_method_for_estimating_the_populations_of_Greek_and_Roman_settlements

So, the density of Rome appears to be 50,000 inhabitants per hectare, about twice of Manhattan. Manhattan's density is not that high compared to the density of some agglomerations in developing countries. The favela Rocinha in Rio de Janeiro has 100,000 inhabitants in 140 hectares, roughly 3 times the density of Manhattan:

Ancient Rome's insulae were perhaps not very different in terms of density, this is a professional reconstruction by the Madrid's museum:

Thanks. That's interesting, but I've got the feeling that we need a construction engineer here to provide  some insight about the use of steel in Brazilian fevalas vs ancient Rome to make multi-storey buildings possible 🙂

Also, what were the crime rates for Rome to match it against similar urban and social organization of modern-day Brazilian favelas?  The comparative numbers for police force, trials and executions will be relevant too.

I assume there could be many citizens who lived outside Rome at the time of Augustus and who either traveled to Rome from the outskirts or were granted a pile of grain the other way

As far I as remember the publication claiming 400,000 dwellers of Rome assumed the number to be the maximum 🙂 Perhaps I shall spare some time to find the paper again, because I read it a few years ago.

Attached is the painting of the baths of Caracalla from todays' post:

https://www.ancient-origins.net/news-history-archaeology/baths-of-caracalla-0016251

The building on the painting seems enormous, a few storeys high, with grand halls. 
But if one looks more carefully, it can be seen that the building basically has only 1 floor. 
The reason for that is simple: Romans were good at producing copious amounts of concrete, but
they never really succeeded in mining and melting iron ore to be able to output the industrial
amounts of steel, which is the essential component for construction beams that are able to withstand
the high load, without which no floor slabs would be possible.
Here is also something I copy from ISO website

https://www.iso.org/obp/ui/#iso:std:iso:6897:ed-1:v1:en

Until this century, buildings were seldom more than a few storeys high and the few tall buildings which did exist were usually of a heavy gravity design which did not readily respond to wind or other forces. Also, tall buildings constructed in the late nineteenth century and early this century generally had vertical load-bearing frames with massive granite infills which provided another generation of unresponsive buildings.

This history of unresponsive building structures has led people to expect buildings to provide nearly stationary accommodation, even under storm conditions, and the occupants of buildings are prepared to accept only extremely low levels of motion.
In contrast to these unresponsive structures, more modern buildings have tended, for reasons of economy of space, foundation reguirements, material outlay, speed of erection and elegance, to be formed from more slender sections such that these much lighter buildings are more responsive to dynamic forces than their predecessors.

 

We are just now seeing a return to low tech mid rise insulae style apt buildings in US:

I mean I strongly suspect that the issue of comparison of ancient Rome with modern Brazilian favelas raised by Guaporense can be attributed to one of the misconceptions or biases: https://en.wikipedia.org/wiki/List_of_cognitive_biases?wprov=sfla1

Such things often happen no matter what science we consider, history or, lets say, astronomy 🙂 In astronomy people often make their judgement about the properties of neutron stars from the position of our earthly experience. In our world a half full glass of boiled water is gonna cool down quicker than the full glass, even if the initial temperature is the same. On neutron stars things work the opposite: the lighter a neutron star is the longer it takes to cool down

On 12/22/2021 at 9:48 AM, Novosedoff said:

As far I as remember the publication claiming 400,000 dwellers of Rome assumed the number to be the maximum 🙂 Perhaps I shall spare some time to find the paper again, because I read it a few years ago.

Among historians specialized in the subject, there are two views: the small Rome view, which states that Rome had about 500,000 to 600,000 inhabitants, and the big Rome view, which states it had around 1 million people or even more.

The small Rome view comes from the fact that Imperial Rome had a walled area of 1,373 hectares which is enough for 500,000 people at twice the density estimated for Pompeii (the city of Pompeii had walls enclosing 66 hectares and a population of around 11,000-12,000).

However, excavations in Ostia, Rome's port city, show that densities much higher than Pompeii were possible, apartment buildings typically had 3-4 floors in there, in Rome proper they were even bigger (bigger cities means taller apartment buildings because land becomes more valuable, Augustus regulated building codes stating heigh limits for insulae at 70 Roman feet, enough for 6-7 floors):

In addition, we know that Augustus' division of Rome into 14 regions covered a substantially larger area than the Aurelian walls (built in the late 3rd century, when the city of Rome had declined in population from its peak during the time of the Late Republic and Early Empire).

Based on the archeological evidence and Augustus', Hanson and Ortman's (2017) model estimates that Rome had 923,000 inhabitants, very close to the 1 million figure typically estimated. (PDF) A systematic method for estimating the populations of Greek and Roman settlements (researchgate.net)

We should also consider that Rome had substantial suburban neighborhoods, as well as ancient writers describe the lack of clear distinction between the city and the countryside, stating that Rome looked like it could stretch forever. The ca. 900,000 figure might be accurate for the city center. Still, there were hundreds of thousands of people living in the suburbs, so Rome's ancient metro area might have approached something like 1.5 million around the 1st century.

Thus, the city of Rome's likely population history in antiquity was:

500 BC: 15,000 (about 30,000 in the city-state, according to Walther Scheidel's estimate in his 2019 book)

300 BC: 90,000 (from Beard (2016), 1 million citizens in the whole city-state)

225 BC: 150,000 (from Keith Hopkins)

30 BC: 900,000 (big jump in growth following the Punic Wars and the conquest of the ancient mediterranean, Rome surpassed Alexandria to be the largest city in the Ancient World, Keith Hopkins estimate Rome approached 1 million people by the time of Augustus)

50 AD: 1,200,000 (perhaps the peak was reached around this time, when they had to build new aqueducts, so population probably increased from Early Augustan period)

275 AD: 600,000 (empire was already in economic and demographic decline during the crisis of the 3rd century, by this time most of the city was enclosed in the 1,373 hectares of the Aurelian walls).

800 AD: 25,000 (population collapse following the fall of the Western Roman Empire, Rome still remained the largest city in Western Europe, with about 20,000 to 30,000 inhabitants, as urban populations collapsed all over Western Eurasia).

19 hours ago, Guaporense said:

Thus, the city of Rome's likely population history in antiquity was:

50 AD: 1,200,000 (perhaps the peak was reached around this time, when they had to build new aqueducts, so population probably increased from Early Augustan period)

 275 AD: 600,000 (empire was already in economic and demographic decline during the crisis of the 3rd century, by this time most of the city was enclosed in the 1,373 hectares of the Aurelian walls).

Interesting assessment. The rather precipitous drop in Rome’s population (50%) between AD 50 and AD 275 is noteworthy.
 

The effects of deadly plagues (including the Antonine Plague in AD 165-180 and the Plague of Cyprian in AD 249-262), as well as the many bloody internecine wars took its toll. It is no surprise that the city of Rome lost its prestige and influence in the Empire during the decades to come.

Well, it's generally agreed by specialists that Classical civilization as a whole (that is, the civilization that was unified under the Roman Empire) started to decline (in economic, technological, and demographic terms) around 100-150 AD. With the economic decline and decline of long-distance trade, cities started to lose population as well, while people migrated to the countryside to live as self-sufficient farmers. This process took several centuries, and the end was the creation of the medieval world.

Rome's population collapse was more dramatic than other cities because it was much bigger (partly thanks to subsidized foot and entertainment paid by the provinces), but it was just part of a general trend: the fact is that it continued to be the largest city in Western Europe until the rise of Cordoba in the 10th century.

2 hours ago, Guaporense said:

 

Well, it's generally agreed by specialists that Classical civilization as a whole (that is, the civilization that was unified under the Roman Empire) started to decline (in economic, technological, and demographic terms) around 100-150 AD

 

I guess the notable exception would be Constantinople. In AD 324 it had a population around 50,000. After it was named the “New Rome” by Constantine, it grew to 500,000. That does not conform with the “general trend of a population collapse.”

They say that regarding the general situation of the ancient world as a whole rather than individual cities. In the case of Constantinople, it grew because the emperor moved the capital there, so it grew much larger, despite the overall decrease in urban population across the empire compared to the level a few centuries earlier.

There’s one problem with this fact though. While the residential population of Manhattan (1.7 million) and the size (22.82 square miles) would mean that only 28K people would fit in one square kilometer, according to https://wagner.nyu.edu/files/rudincenter/dynamic_pop_manhattan.pdf, about 4 million workers stay at the city during a weekday, declining to about 2 million at night. That’s still more then the residential population. This also means that over 65K people are in one square kilometer (that’s way more then Rome’s suspected population density of 40-50K) and over 170K per square mile (bigger then the 70K said). Plus, Midtown and Lower Manhattan are full of skyscrapers were people work meaning that the density is higher then the few tens of thousand that live in both districts (Possibly over 700K in Midtown alone!). So, in reality, Manhattan is most likely even more dense then Ancient Rome!