Marbleezy asks: How did the ancient Romans manage to build perfectly straight roads hundreds
of miles long?
The ancient Romans were a people famed for their architectural prowess, something no
better demonstrated than by their ability to build almost perfectly straight and incredibly
durable roads spanning expansive distances.
For example, in Britain alone, the Romans built well over 50,000 miles of roads with
the longest ruler-straight stretch spanning over 50 miles.
They did all of this in an era without modern surveying tools, construction equipment, or
even very accurate maps of precisely where their destination was for many of the areas.
So how did they do it?
To begin with, it's important to note there were a few different types of roads that were
made throughout the Roman Republic and Empire, and exact method and materials used for road
construction varied somewhat from region to region and evolved slightly over the centuries.
That caveat out of the way, the three main classification of Roman roads were viae terrenae,
essentially dirt roads, often made by people walking and wagons riding over the same path
over time; viae glareae, which would be a dirt road that was then graveled; and, finally
much more interestingly, viae munita, which were more or less paved roads, some of which
have survived through modern times.
Within these types of roads there were further classifications based on who could use them,
such as viae publicae (public roads), viae militares (military or state use roads), and
viae privatae (private roads, constructed at private expense and for the owners to decide
who they allowed access, perhaps the general public or perhaps just a select few).
To help pay for them, roads of all types often had tolls, particularly at locations like
bridges and city gates where it would be impractical to avoid the tolling location.
This brings us to the road construction process itself.
As dirt and gravel roads aren't terribly interesting, we're going to focus this article on the viae
munita.
So how did they make these incredibly durable and generally amazingly straight roads?
After all, even with modern machinery, constructing and maintaining an expansive road system is
an extremely time consuming and labor intensive process.
To start with, a group of surveyors would be sent out to figure out the precise direction
connecting the two main points.
At the same time, they'd attempt to plan the route as efficiently as possible while accounting
for any major obstacles like tall mountains, rivers, etc.
When possible, they may attempt to avoid such obstacles, but, particularly in some of the
earliest Roman road construction, where it might result in having to take a large detour
to get around, say, a mountain, if possible given the terrain, they tended to just build
the road to go directly over it or directly through it.
For example, the longest tunnel through such a mountain was the Grotta di Cocceio which
was excavated from 38 to 36 BCE and is approximately 1 km (.62 miles) long and about 5 meters (5.4
yards) high and wide.
Before WWII, it was also still a fully functional and safe to traverse tunnel despite standing
about 2,000 years at that point, but was damaged during the war, though there are presently
efforts to have it repaired and opened again to the public.
As for going over a mountain, it's important to note here that we don't mean they'd use
switch backs as is the general method today.
No, if at all possible, they'd just build roads straight up a mountain and down the
other side, expecting the soldiers and mules and the like to just man up and traverse the
steep slopes without complaint.
That said, as the empire matured, it did eventually become apparent that there were economic advantages
to slightly longer roads that were easier for draught animals to pull carts over, and
thus there was a shift to favoring longer distances but lesser gradients when talking
roads for general public use.
Either way, during the process, the surveyors would setup markers, often at very visible
points like on hills, mapping out the optimal path, again trying to ensure the road would
be as straight as possible between the start and end point to reduce needed labor, materials,
and distance needed to traverse the road once it was complete.
This brings us to how they actually ensured perfectly straight roads between the markers.
A key tool here was a device known as a groma.
In a nutshell, this was nothing more than a sort of cross with four weights hanging
from a string at each end of the cross to function as plumb lines.
The whole thing could rotate with degree markers on top.
Two of the plumb lines would then be lined up with a marker and then on the other side
lined up with the previous marker.
Where changes in direction would need to be made, the degrees were marked and ultimately
the whole thing drawn up on a central document showing the entire route of the road with
each segment.
Once the actual construction was to begin, the groma would once again be used, this time
with rods pounded into the ground between markers using the groma to make sure every
single rod was perfectly inline in between the markers.
Now, finally, construction of the road would start, usually first done via plows to loosen
the soil, this would be followed by legionaries and/or slaves digging the ground out, with
depth varying based on conditions.
For instance, swampy land would need a lot thicker foundation if it was to have any staying
power.
For more typical ground, the trench needed would be somewhere in the realm of 3-6 feet
(around 1-2 meters) deep.
Once dug out, this would then be tamped down to a leveled, compact layer of earth.
From here, exact road composition varied based on available materials in a given region,
land composition, and a variety of factors like this.
But typically large stones would be packed as tightly as possible together and into the
earth base.
Onto this layer would usually be placed smaller stones, sometimes comprising broken concrete
or somewhat crushed rock, again packed and smoothed as best as possible.
Depending on availability, they would also put a layer of sand on this foundation to
make a genuinely perfectly smooth surface.
On top of all of this, at the minimum gravel would be added, packed, and leveled.
In some cases, such as near big cities, as described in one manuscript on the construction
of roads in Rome itself, paving stones, often flint, lava rock, or marble, would be embedded
in cement for the top layer instead.
When the road was complete, they are thought to have been quite smooth allowing for relatively
bump free travel in carts and the like.
During this whole process, special attention was taken to making the center of the road
higher than the sides so that any water would drain off, with the entire road surface itself
also elevated above the ground on the sides where drainage ditches would generally be
created to help rapidly move water away from the road in times of heavy rains.
As for the size of the roads, according to something known as The Law of Twelve Tables,
which more or less formed the basis of Roman Law for almost a millennia, Roman roads were
required to be at minimum 8 Roman feet wide (which converted into modern units equals
about 2 and half metres) where the road was straight and double that if the road happened
to be curved.
Beside the roads were footpaths, sometimes graveled, which were particularly handy in
the case of viae militares where only people with proper authorization could use the road
itself.
Finally, at the very outer edges of the roads, any nearby trees and bushes would be removed
to help reduce areas for bandits to hide and surprise anyone with an attack, as well as
to help ensure plant growth didn't overtake the road or tree roots compromise it.
But this wasn't the end of the construction process.
They now needed to know exact distances along the road.
It's not fully clear how they did this, though a device known as the odometer of Vitruvius
is mentioned starting around 27 BC and is often claimed to have been used for this purpose.
However, whether it was actually ever used for road construction, or even made at all,
is up for debate.
At a high level, this device used the spinning of a wheel to mark distance.
In this case, it was the spinning of a wagon wheel which was in turn hooked up to gears
that would drop a pebble into a container every Roman mile (4,841 feet, which is around
1,000 paces of an adult male, with the world "mile" deriving from the Latin milia, meaning,
funny enough, 1,000 paces).
For whatever it's worth, while Leonardo da Vinci tried and failed to make such a device
as per outlined, in 1981 one Andre Sleeswyk was successful in building one exactly as
described except, unlike da Vinci, he used triangular gear teeth instead of square ones.
His justification for this modification being that these same type of gear teeth were used
in the Antikythera mechanism, which was created sometime from around 250 BC to 70 BC, with
the device itself used to predict various astronomical phenomenon like eclipses.
Thus, perhaps if the odometer of Vitruvius was ever actually built and used, maybe it
used these too.
There are, of course, many other much less technologically advanced ways they could have
measure mile distances easy enough and with extreme accuracy.
However they did it, at every mile mark, the law required they place an approximately two
ton, 7 foot tall (2 feet in the ground) mile marker, called a miliarium.
Helpfully, on this stone would be engraved the names of the locations the road connected
and how many miles to each from that respective marker.
A master marker, known as the Miliario Aureo or Golden Milestone was also created during
Caesar Augustus' rule and placed in the central Forum of Rome itself.
This was the point at which all Roman roads were said to lead.
It's not actually clear what was on this master marker, but it's been speculated it listed
the distances from that point to all major cities under Roman rule.
Whatever the case, like the roads themselves, some of these mile markers are still standing
giving archaeologists and historians a valuable snapshot of the past, since they tended to
include not just basic geographic information, but information about when the road was built
or repaired and by whom.
Next up, it was also required by law that regular way stations be built for official
use, generally every 16 to 19 miles apart.
These were more or less really nice resting areas providing food and drink and the like
for officials.
For the general public, inns known as cauponae would tend to pop up near these way stations.
On that note, at particularly high trafficked way stations, many other businesses would
pop up as well, sometimes leading to the creation of whole towns.
Along these roads you'd also find at similar intervals mutationes, or changing stations,
where people could get the services of veterinarians, wheelwrights, etc., as well as potentially
find new mounts.
To give you an idea of how fast one could move along these roads with its network of
way stations and facilities, it's noted that Emperor Tiberius once traversed about 200
miles in 24 hours after news that his brother, Drusus Germanicus was dying from gangrene
after being seriously injured falling from a horse.
A more typical time to traverse for, say, a government mail carrier was usually around
50 miles per day if not in a particular hurry.
But to sum up, it turns out that Roman road construction, amenities and all, wasn't all
that different from modern times, often featuring deep foundations, paved surfaces, proper drainage,
landscaping around the roads, sidewalks, toll booths, rest areas, hotels, restaurants, the
historic equivalent to gas stations and convenience stores, etc.
In short, the Ancient Romans were pretty brilliant in a lot of ways…
Speaking of being Brilliant…
BRILLIANT!...
Bonus Fact: The infamous phrase—“Nero fiddled while
Rome burned”—has come to mean a person who is neglecting their duties, probably by
doing something frivolous.
But did Nero actually sit around play music while Rome was burning around him in 64 AD?
To begin there was such a fire, though its extent is unknown.
According to Tacitus, the fire lasted for six days and decimated Rome, with only four
districts untouched (out of a total of fourteen).
He goes on to state that ten of the eleven districts that burned were heavily damaged,
with three of those completely destroyed.
However, oddly, there is very little documented mention of the fire from those who actually
lived through it.
The only Roman historian during that period who even mentioned it at all was Pliny the
Elder, and even he only briefly referenced it in passing.
Had it been as widespread as Tacitus claimed, one would think the likes of Plutarch, Epictetus,
or other such famed Roman historians who lived through the fire would have mentioned such
a significant event.
And, indeed, we see that perhaps it wasn't that great of a fire from the only other documented
first hand account of the scope of the disaster- a letter from Seneca the Younger to Paul the
Apostle, where he explicitly stated that only four blocks of insulae were burned (a type
of apartment building), along with 132 private houses damaged (about 7% of the private houses
in the city and .009% of the insulae).
Not anywhere close to as widespread as Tacitus later claimed, though Seneca did say the fire
lasted six days, as Tacitus stated.
As to Nero's reaction to the fire, the first and biggest flaw in the fiddling story is
that the fiddle, or violin, didn’t actually exist in Nero’s time.
Historians aren’t able to give an exact date for the invention of the violin, but
the viol class of instruments to which the violin belongs wasn’t developed until at
least the 11th century.
If Nero actually did play a stringed instrument—and there’s no evidence that he did, whether
during the burning of Rome or otherwise—it was probably a lyre or cithara.
Okay, so some details can get muddled through history.
But did Nero neglect Rome while it burned?
Historians argue probably not.
Reports do place Nero thirty-five miles away from Rome at the time of the fire, as he was
staying in his villa at Antium.
However, an account from Tacitus tells us that he returned to Rome immediately when
word of the fire reached him in order to begin relief efforts.
As the fire raged on, Nero even opened up his own gardens to provide a temporary home
for those who were now homeless.
He also ordered the construction of emergency accommodation and cut the price of corn, as
well as provided food directly, so that people could eat.
Besides this, he paid for much of these relief efforts out of his own pocket.
However, Tacitus also tells of the rumour that had spread among the masses: while the
flames surged through the city, Nero stood on his private stage and sang about the destruction
of Troy in a comparison of the two events.
Whether or not the rumour had any evidence to back it up or was just something made up
by the unhappy masses, we don’t know, but this and Suetonius' account are the most likely
source of the fiddle story we hear today.
Unfortunately for Nero, at least in the context of this story, he did have a reputation for
enjoying concerts and participating in music competitions, so the activity itself wasn’t
entirely unlikely even if the timing of the act is highly questionable.
While Tacitus claims the singing story was a rumour, Suetonius wrote about it with conviction.
However, the story could have been an attempt to further mar Nero’s name.
Nero faced problems during his reign from the very start, when it was reported that
his own mother poisoned his predecessor, Claudius.
He was also blamed for the death of Claudius’ son Brittanicus, who was being urged to take
his proper place as Emperor by overthrowing Nero.
Numerous other deaths were thought to have been committed by Nero’s hand, including
one of his wives and his own mother.
As such, Nero was painted as a man who was difficult for the masses to trust.
No one knew how the fire started, and many Romans believed that he had started the fire
that burned their city.
(It likely started in shops containing flammable goods, and was probably an accident rather
than any one person’s intentional act.)
With the mob out for blood, Nero was forced to turn to a scapegoat and blamed Christians
for starting the fire.
There were only a small number of Christians in Rome at the time and they were considered
a strange religious sect, so they were an easy target.
As Tacitus stated: “Consequently, to get rid of the report,
Nero fastened the guilt and inflicted the most exquisite tortures on a class hated for
their abominations, called Christians by the populace.
Christus, from whom the name had its origin, suffered the extreme penalty during the reign
of Tiberius at the hands of one of our procurators, Pontius Pilatus, and a most mischievous superstition,
thus checked for the moment, again broke out not only in Judæa, the first source of the
evil, but even in Rome, where all things hideous and shameful from every part of the world
find their centre and become popular.
Accordingly, an arrest was first made of all [Christians] who pleaded guilty [to the fire];
then, upon their information, an immense multitude was convicted, not so much of the crime of
firing the city, as of hatred against mankind.
Mockery of every sort was added to their deaths.
Covered with the skins of beasts, they were torn by dogs and perished, or were nailed
to crosses, or were doomed to the flames and burnt, to serve as a nightly illumination,
when daylight had expired.”
Even finding someone to blame for the fire didn’t help Nero’s plea of innocence.
In the wake of the fire, he built a palace on top of some of the land cleared by the
flames, which people argued he had been planning from the start, though this is highly unlikely
as the place he built the new palace was over a half mile away from where the fire started.
In addition to a new palace, Nero did provide for the reconstruction of the city, but rebuilding
stretched the limits of Rome’s treasury at the time.
He was forced to devalue Roman currency, which wasn’t a popular move.
Nero ended up committing suicide—or at least, begging his secretary to kill him when he
lost the nerve to do it himself—four years after the fire.
Accounts of his life and of the time of the fire are highly contradictory.
Further, Suetonius and Tacitus wrote their histories fifty years after Nero died, and
Cassius Dio wrote his 150 years later.
Many historians also think it likely that Nero was more popular with the people of Rome
than he was with the senators, and as all three of the main sources were from the senatorial
class, it’s likely they carry more than a little bias against him, not unlike happened
with the popular history of Marie Antoinette who popular history remembers very differently
than who the actual woman appeared to be.
That being said, Tacitus did state that while Nero’s death was welcomed by senators, the
lower classes mourned his passing.
So in the end, the implication that “Nero fiddled while Rome burned”—or played the
lyre, sang a song, or neglected his duty in any way—is likely the result of anti-Nero
propaganda and an attempt to tarnish his name.
The morality of many of his actions during his reign is open to debate, but the fiddling,
or playing music, story is almost certainly a myth, unless he was playing to entertain
the displaced masses he'd taken in.