The Romans thought big.
Their empire included a quarter of the world’s population.
Their capital was the largest city anywhere on the planet before the nineteenth century.
They floated hundred-ton obelisks across the Mediterranean, staged campaigns from Scotland
to Sudan, and stained the Greenland Ice Cap with the residue of their silver mines.
The Romans were especially adept at gigantic construction projects.
Some of these are famous, like the Colosseum, with its underworld of tunnels and cages,
or the Circus Maximus, which could fit a quarter-million spectators.
Hadrian’s Wall – the 73-mile barrier of turf and stone that still spans northern England
– is equally well-known.
In one of my older videos, I talked about a few lesser-known Roman megaprojects, such
as Nero’s spectacular dams at Subiaco and the towering Temple of Hadrian at Cyzicus.
In this video, I’ll continue that theme by exploring three of the most impressive
examples of Roman engineering you’ve probably never heard of.
So, without any further ado…
Number 3.
The Tunnel of Claudius Fucinus Lacus – the Fucine Lake – was
a large lake in central Italy, about 50 miles east of Rome.
The land around it was exceptionally fertile.
But since the lake had no natural outlet, its depth fluctuated, alternately drowning
and deserting the villages and fields on its shores.
Julius Caesar considered a project to control the lake, and Augustus was urged to do so
by the local inhabitants.
But it was only during the reign of the rather hapless emperor Claudius that work finally
got underway to connect the Fucine Lake with the nearest river.
Fortunately, a river – the Liris – ran only five miles from the lakeshore.
Less conveniently, a thousand-foot limestone mountain stood between river and lake.
Claudius ordered a tunnel to be driven through the mountain, and 30,000 men set to work.
As they proceeded, forty vertical shafts were driven down through the mountain, to ventilate
the tunnel and allow baskets of stone to be hauled up to the surface.
After eleven years, the tunnel was done: ten feet high, five feet wide, and three and a
half miles long – the longest tunnel constructed anywhere before the late nineteenth century.
To celebrate its opening, Claudius staged a mock naval battle on the Fucine Lake, in
which 19,000 slaves and condemned criminals fought.
(The shores were patrolled by squadrons of marines with catapults and ballistae, to prevent
any escapes.)
The emperor was so impressed by the valor of the combatants that he rescinded the death
sentences of those who survived the battle.
Then the tunnel was opened.
It turned out the level of the floor had been set a few feet too high, and the lake refused
to drain.
Undaunted, Claudius ordered the tunnel deepened.
This was done; and a second grand opening was staged, during which gladiators fought
on fleets of rafts anchored in the lake.
A banquet was laid out near the tunnel mouth, with Claudius and Empress Agrippina, resplendent
in cloth of gold, in the seats of honor.
With great fanfare, the tunnel was opened again.
This time, it worked all too well.
Water surged into the river, bringing it to flood stage.
As the river rose, it swallowed the banquet tables, drowning many diners.
The emperor narrowly escaped with his life.
Claudius’ tunnel remained in operation for several centuries.
During late antiquity, however, it became clogged, and the Fucine Lake rose to its former
level.
Despite repeated attempts to reopen the tunnel during the Middle Ages and Renaissance, it
was not until the mid-nineteenth century, and only with the aid of steam shovels and
explosives, that the lake was finally drained.
Number Two.
The Iron Gates Highway About three-quarters of the way down the Danube’s
eighteen-hundred-mile course, along the modern frontier of Serbia and Romania, the banks
of the river – pinched by the foothills of two mountain chains – rise into majestic
cliffs.
The channel between contracts; and until the twentieth century, when a series of dams was
constructed, the compressed river roared over dangerous rapids.
These are the Iron Gates of the Danube.
In the reign of Augustus, the Romans pushed their Balkan frontier to the south bank of
the Danube.
North of the river lay the hostile kingdom of Dacia, from which raiding parties armed
with razor-sharp scimitars descended on the villas and villages of the empire.
Finally, just after the turn of the second century, the emperor Trajan decided to end
the Dacian threat.
As part of the preparations for Trajan’s first Dacian War, a military highway was driven
through the Iron Gates of the Danube.
For miles, where the cliffs rose sheer from the rapids, half the roadbed was hacked into
the rockface.
The other half was supported by huge beams that projected over the rushing water.
At the end of the rock cutting, Trajan’s engineers carved the so-called Tabula Traiana
to celebrate their construction of a road that had (to paraphrase the inscription) been
cut through mountains and suspended over streams.
Long canals were dug along the highway to allow boats to bypass the rapids.
The most impressive part of the local transportation network, however, stood just below the gates,
where Trajan’s engineers constructed the greatest of all ancient bridges.
Twenty colossal piers of stone and concrete rose sixty feet above the river’s surface.
Between them, poised atop huge wooden trusses, was a roadway more than two-thirds of a mile
long – the longest bridge, and the bridge with the widest spans between its piers, to
that point in history.
Although the wooden deck was removed in late antiquity, the piers of Trajan’s Bridge
stood well into the Middle Ages.
The foundations survived into the early twentieth century, when they were dynamited to make
room for a new shipping channel.
Unfortunately, only the approaches of the great bridge can still be seen today; everything
else, along with the rest of Trajan’s highway through the Iron Gates, has been covered by
the waters of a reservoir.
Number One.
The secret harbor at Lake Avernus Lake Avernus – the Lago d’Averno – lies
in the pit of a dead volcano just west of Naples.
The first Greek explorers thought it an eerie place, its banks darkened by tangled woods,
its waters mantled with poisonous fog.
No bird, it was said, could fly over Avernus and live.
Just south of Avernus was the Lucrine Lake, a brackish lagoon separated from the Bay of
Naples by a narrow strip of sand.
The water was warm and splashed with sun; countless oysters speckled the sandy bottom.
A few years after the assassination of Julius Cesar, this picturesque pair of lakes was
transformed on the orders of Octavian – the ruthless young warlord who would, more than
a decade later, rename himself Augustus.
Octavian was embroiled in a war with Sextus Pompeius, the last surviving son of Pompey
the Great, who had seized Sicily and was raiding up and down the coasts of Italy.
To defeat Sextus Pompeius, Octavian needed an efficient navy; and to train that navy,
he required a port that would be sheltered from storms and concealed from the enemy.
To those ends, he asked Marcus Agrippa, his best friend and best lieutenant, to build
a new harbor.
Agrippa realized that Lake Avernus and the Lucrine Lake, close to each other and to the
Bay of Naples, could be linked to create a harbor complex invisible to Sextus Pompeius’
patrols.
After bracing the shores of the Lucrine Lake with a massive seawall, he connected the lake
with the sea by a guarded channel, and cut a canal from the Lucrine Lake to Lake Avernus.
To facilitate overland travel between the new port and the neighboring towns, Agrippa
ordered the engineer Lucius Cocceius Auctus to drive a series of tunnels through the rocky
ridges surrounding the lakes.
The most impressive of these, known today as the Grotta di Cocceio, was nearly a kilometer
long and wide enough for two fully-loaded wagons.
It remained in use until the Second World War, when retreating Nazis touched off explosives
that had been stored inside.
Agrippa’s new harbor complex worked exactly as intended.
With characteristic efficiency, he constructed a new fleet, trained 20,000 men as marines
and rowers, performed naval exercises in the shelter of the lakes, and finally – in 36
BC – sailed out into the Bay of Naples to engage the fleet of Sextus Pompeius.
A few months later, Agrippa won the Battle of Naulochus, ending the war.
Not long after, the Roman western fleet moved to nearby Misenum, and Agrippa’s harbor
was abandoned.
Despite some silting, it seems to have retained its ancient shape until 1538, when a sudden
volcanic eruption created a 600-foot hill – the so-called Monte Nuovo – in only
two days.
Much of the Lucrine Lake was buried.
It's still possible, however, to stroll around Lake Avernus and see, among the trees and
whitewashed modern villas, the broken brick and concrete walls of Agrippa’s harbor,
a forgotten Roman megaproject.
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