Dry As Dust

A Fortean in the Archives

A visit to the underworld: the unsolved mystery of the tunnels at Baiae

and the Bay of Naples, painted by J.M.W. Turner in 1823, well before
modernization of the area obliterated most traces of its Roman past.
Image: Wikicommons.

There is nothing remotely Elysian about the Phlegræan Fields, which
lie on the north shore of the Bay of Naples; nothing sylvan, nothing
green. The Fields are part of the caldera of a volcano that is the twin
of Mount Vesuvius, a few miles to the east, the destroyer of Pompeii.
The volcano is still active–it last erupted in 1538, and once possessed
a crater that measured eight miles across–but most of it is underwater
now.  The portion that is still accessible on land consists of a barren,
rubble-strewn plateau. Fire bursts from the rocks in places, and clouds
of sulfurous gas snake out of vents leading up from deep underground.

Fields, in short, are hellish, and it is no surprise that in Greek and
Roman myth they were associated with all manner of strange tales. Most
interesting, perhaps, is the legend of the Cumæan sibyl, who took her name from the nearby town of Cumæ, a Greek colony dating to about 500 B.C.– a time when the Etruscans still held sway much of central Italy and Rome was nothing but a city-state ruled over by a line of tyrannical kings.

Renaissance-era depiction of a young Cumæan sibyl by Andrea del
Catagno. The painting can be seen in the Uffizi Gallery. Image:

The sibyl, so the story goes, was a woman
named Amalthaea who lurked in a cave on the Phlegræan Fields. She had
once been young and beautiful–beautiful enough to attract the attentions
of the sun god, Apollo,
who offered her one wish in exchange for her virginity. Pointing to a
heap of dust, Amalthaea asked for a year of life for each particle in
the pile, but (as is usually the way in such old tales) failed to allow
for the vindictiveness of the gods. Ovid, in Metamorphoses, has her lament that
"like a fool, I did not ask that all those years should come with
ageless youth, as well." Instead, she aged but could not die. Virgil
depicts her scribbling the future on oak leaves that lay scattered about the entrance to her cave, and states that the cave itself concealed an entrance to the underworld.

best-known–and from our perspective the most interesting–of all the
tales associated with the sibyl is supposed to date to the reign of Tarquinius Superbus–Tarquin
the Proud. He was the last of the mythic kings of Rome, and some
historians, at least, concede that he really did live and rule in the
sixth century B.C. According to legend, the sibyl traveled to Tarquin’s
palace bearing nine books of prophecy that set out the whole of the
future of Rome. She offered the set to the king for a price so enormous
that he summarily declined–at which the prophetess went away, burned the
first three of the books, and returned, offering the remaining six to
Tarquin at the same price. Once again, the king refused, though less
arrogantly this time, and the sibyl burned three more of the precious
volumes. The third time she approached the king, he thought it wise to
accede to her demands. Rome purchased the three remaining books of
prophecy at the original steep price.

What makes this story of
interest to historians as well as folklorists is that there is good
evidence that three Greek scrolls, known collectively as the Sibylline
Books, really were kept, closely guarded, for hundreds of years after
the time of Tarquin the Proud. Secreted in a stone chest in a vault
beneath the Temple of Jupiter,
the scrolls were brought out at times of crisis and used, not as a
detailed guide to the future of Rome, but as a manual that set out the
rituals required to avert looming disasters. They served the Republic
well until the temple burned down in 83 B.C., and so vital were they
thought to be that huge efforts were made to reassemble the lost
prophecies by sending envoys to all the great towns of the known world
to look for fragments that might have come from the same source. These
reassembled prophecies were pressed back into service and not finally
destroyed until 405, when they are thought to have been burned by a
noted general by the name of Flavius Stilicho.

drifts from a vent on the barren volcanic plateau known as the
Phlegraean Fields, a harsh moonscape associated with legends of
prophecy. Photo: Wikicommons.

The existence of the
Sibylline Books certainly suggests that Rome took the legend of the
Cumæan sibyl seriously, and indeed the geographer Strabo, writing at
about the time of Christ, clearly states that there actually was "an Oracle of the Dead
somewhere in the Phlegræan Fields. So it is scarcely surprising that
archaeologists and scholars of romantic bent have from time to time gone
in search of a cave or tunnel that might be identified as the real home
of a real sibyl–nor that some have hoped that they would discover an
entrance, if not to Hades, then at least to some spectacular
subterranean caverns.

Over the years several spots, the best known of which lies close to Lake Avernus, have been identified as the antro della sibilla–the
cave of the sibyl. None, though, leads to anywhere that might
reasonably be confused with an entrance to the underworld. Because of
this, the quest continued, and gradually the remaining searchers focused
their attentions on the old Roman resort of Baiæ
(Baia), which lies on Bay of Naples at a spot where the Phlegræan
Fields vanish beneath the Tyrrhenian Sea. Two thousand years ago, Baiæ
was a flourishing spa, noted both for its mineral cures and for the
scandalous immorality that flourished there. Today, it is little more
than a collection of picturesque ruins–but it was there, in 1932, that
the entrance to a hitherto unknown antrum was discovered, concealed behind a recently installed pizza oven.

The entrance to the bizarre tunnel system known, after Robin Paget, as the Antrum of Initiation at Baiæ.

The antrum at
Baiæ proved difficult to explore. A sliver of tunnel, obviously ancient
and manmade, disappeared into a hillside close to the ruins of a
temple. The first curious onlookers who pressed their heads into its
cramped entrance beat a hurried retreat–the pitch-black passageway was
uncomfortably hot and wreathed in sulfurous smoke. There the mystery
rested while the Second World War intervened, and it was not revived
until, early in the 1950s, the site came to the attention of Robin

Paget was not a professional archaeologist. He was a Briton
who worked at a nearby NATO airbase, lived in Baiæ, and excavated
mostly as a hobby. As such, his theories need to be viewed with caution,
and it is worth noting that when the academic Papers of the British School at Rome
agreed to publish the results of the decade or more that he and an
American colleague named Keith Jones spent digging in the tunnel, a firm
distinction was drawn between the School's endorsement of a
straightforward description of the findings and its refusal to pass
comment on the theories Paget had come up with to explain his perplexing
discoveries. These theories eventually made their appearance in book
form but attracted little attention–surprisingly, because the pair
claimed to have stumbled across nothing less than a real-life "entrance
to the underworld."

Paget was one of the handful of men who still
hoped to locate the “cave of the sibyl” described by Virgil, and it was
this obsession that made him willing to risk the inhospitable interior.
He and Jones pressed their way though the narrow opening that had lain
concealed behind the oven and found themselves inside a high but narrow
tunnel, eight feet tall but just 21 inches wide. The temperature inside
was uncomfortable but bearable, and although the airless interior was
still tinged with volcanic fumes, the two men pressed on into a passage
that, they claimed, had probably not been entered for 2,000 years.

A plan of Baiae's mysterious "Oracle of the Dead," showing the complex layout of the tunnels and their depth below ground level.

the tunnel downward, Paget and Jones calculated that it fell only
around 10 feet in the first 400 feet of its length before terminating in
a solid wall of rubble that blocked the way. But even the scanty
evidence the two men had managed to gather during this early phase of
their investigation persuaded them that it was worth pressing on. For
one thing, the sheer amount of spoil that had been hauled into the
depths suggested a considerable degree of organization–years later, when
the excavation of the tunnel was complete, it would be estimated that
700 cubic yards of rubble, and 30,000 man-journeys, had been required to
fill it. For another, using a compass, Paget determined that the
mysterious passage had been oriented to the sunrise on midsummer’s day.
This suggested that it served some ritual purpose.

It took Paget
and Jones, working in difficult conditions with a small group of
volunteers, the beter part of a decade to clear and explore what turned
out to be a highly ambitious tunnel system. Its ceremonial function
seemed to be confirmed by the existence of huge numbers of niches for
oil lamps–they occurred every yard in the tunnels’ lower levels, far
more frequently than would have been required merely to provide
illumination. The builders had also given great thought to the layout of
the complex, which seemed to have been designed to conceal its

"River Styx"–an underground stream, heated almost to boiling point in
places, which runs through at the deepest portions of the tunnel
complex. It was the discovery of this stream that led Paget to formulate
his daring hypothesis that the Great Antrum was intended as a
representation of the mythic underground passageways to Hades.

the portion of the tunnels choked by rubble, Paget and Jones found,
hidden behind an S-bend, a second blockage. This, the explorers
discovered, marked the place where two tunnels diverged. Basing his
thinking on the remains of some ancient pivots, Paget suggested that the
spot had at one time harbored a concealed door. Swung closed, this
would have masked the entrance to a second tunnel that acted as a
short-cut to the lower levels. Opened partially, it could have been used
(the explorer suggested) as a remarkably effective ventilation system;
hot, vitiated air would be sucked out of the tunnel complex at ceiling
level, while currents of cooler air from the surface were constantly
drawn in along the floor.

But only when the men went deeper into
the hillside did the greatest mystery of the tunnels revealed itself.
There, hidden at the bottom of a much steeper passage, and behind a
second S-bend that prevented anyone approaching from seeing it until the
final moment, ran an underground stream. A small “landing stage”
projected out into the sulfurous waters, which ran from left to right
across the tunnel and disappeared into the darkness. And the river
itself was hot to the touch–in places it approached boiling point.

at this low point in the tunnel complex certainly were stygian. The
temperature had risen to 120 degrees Fahrenheit; the air stank of
sulfur. It was a relief to force a way across the stream and up a steep
ascending passage on the other side, which eventually opened into an
antechamber, oriented this time to the helical sunset, that Paget dubbed
the “hidden sanctuary.” From there, more hidden staircases ascended to
the surface to emerge behind the ruins of water tanks that had fed the
spas at the ancient temple complex.

Phlegræan Fields (left) and Mount Vesuvius, after Scipione Breislak's
map of 1801. Baiae lies at the northeastern tip of the peninsula of
Bacoli, at the extreme westerly end of the Fields.

was this “Great Antrum,” as Paget dubbed it? Who had built it–and for
what purpose? And who had stopped it up? After a decade of exploration,
he and Jones had formulated answers to those questions.

The tunnel
system, the two men proposed, had been constructed by priests to mimic a
visit to the Greeks' mythical underworld. In this interpretation, the
stream represented the fabled River Styx, which the dead had to cross to
enter Hades; a small boat, the explorers speculated, would have been
waiting at the landing stage to ferry visitors across. On the far side
these initiates would have climbed the stairs to the hidden sanctuary,
and it was there they would have met... who? One possibility, Paget
thought, was a priestess posing as the Cumæan sibyl, and for this reason
he took to calling the complex the "Antrum of Initiation."

tunnels, then, in Paget's view, might have been constructed to allow
priests to persuade their patrons–or perhaps simply wealthy
travelers–that they had traveled through the underworld. The scorching
temperatures below ground and the thick drifts of volcanic vapor would
certainly have given that impression. And if visitors were tired,
befuddled or perhaps simply drugged, it would have been possible to
create a powerfully otherworldly experience capable of persuading even
the skeptical.

A general plan of the tunnel complex, drawn by Robin Paget. Click twice to view in higher resolution.

favor of this argument, Paget went on, was the careful planning of the
tunnels. The "dividing of the ways," with its hidden door, would have
allowed a party of priests–and the "Cumæan sibyl" too, perhaps–quick
access to the hidden sanctuary, and the encounter with the "River Styx"
would have been enhanced by the way the tunnels' S-bend construction
concealed its presence from new initiates. The system, furthermore,
closely matched ancient myths relating visits to the underworld. In
Virgil's Aeniad, for instance, the hero, Aeneas, crosses the
Styx only once on his journey underground, emerging from Hades by an
alternate route. The tunnel complex at Baiæ seemed to have been
constructed to allow just such a journey–and Virgil, in Paget's
argument, had lived nearby and might himself have been an initiate in
Baiæ's mysteries.

Dating the construction of the complex was a
greater challenge. The explorers found little evidence inside the
tunnels that might point to the identity of the builders–just a mason's
plumb bob in one of the niches and some ancient graffiti. But, working
on the assumption that the passages had formed part of the surrounding
temple complex, they concluded that they could best be dated to the late
archaic period around 550 B.C.–at pretty much the time, that is, that
the Cumæan sibyl was said to have lived. If so, the complex was was
almost certainly the work of the Greek colonists of Cumæ itself. As for
when the tunnels had been blocked up, that–Paget thought–must have taken
place after Virgil's time, during the early Imperial period of Roman
history. But who exactly ordered the work, or why, he could not say.

time, Paget and Jones solved at least some of the Great Antrum's
mysteries. In 1965 they persuaded a friend, Colonel David Lewis of the
U.S. Army, and his son to investigate the Styx for them using scuba
apparatus. The two divers followed the stream into a tunnel that
dramatically deepened and discovered the source of its mysterious heat:
two springs of boiling water, superheated by the volcanic chambers of
the Phlegræan Fields.

of the two boiling springs that feed the "Styx," photographed in 1965,
250 feet beneath the surface, by Colonel David Lewis, U.S. Army.

Paget and Jones's elaborate theories are correct remains a matter of
debate. That the tunnel complex served some ritual purpose can hardly be
doubted if the explorers' compass bearings are correct, and the
specifics of its remarkable construction seem to support much of what
Paget says; the alternative explanation–that the tunnel was dug by the
Roman army and once lead to a subterranean restaurant–seems to be
considerably more far fetched. In particular, it is hard to see the
channel of boiling water deep underground as anything other than a
deliberate representation of one of the fabled rivers that girdled
Hades–if not the Styx itself, then perhaps the Phlegethon, the mythic "river of fire" that, in Dante's Inferno,
boils the souls of the departed. Historians of the ancient world do not
dispute that powerful priests were fully capable of mounting elaborate
deceptions–and a recent geological report
on the far better known Greek oracle site at Delphi demonstrated that
fissures in the rocks nearby brought intoxicating and anaesthetic gases
to the surface at that spot, suggesting that it may have been selected
and used for a purpose much like the one Paget proposed at Baiæ.

much remains mysterious about the Great Antrum–not least the vexed
question of how ancient builders, working with primitive tools at the
end of the Bronze Age, could possibly have known of the existence of the
"River Styx," much less excavated a tunnel that so neatly intercepted
it. There is no trace of the boiling river at the surface–and it was not
until the 1970s, after Paget's death, that his collaborators finally
discovered, by injecting colored dyes into its waters, that it flows
into the sea miles away, on the northern side of Cape Miseno.

found one foot-high fragment of roughly painted graffiti close to the
entrance of the tunnels. He interpreted the first line to read "Illius"
("of that"), and the second as a shorthand symbol representing a prayer
to the Greek goddess Hera.

Little seems to have
changed at Baiæ since Paget's day. His discoveries have made remarkably
little impact on tourism at the ancient resort, and even today the
network of passages he worked so long to clear remain locked and barely
visited. A local guide can be hired,
but the complex remains difficult, hot and uncomfortable to visit.
Little attempt is made to exploit the idea that it was once thought to
be an entrance to the underworld, and, pending reinvestigation by
trained archaeologists, not much more can be said about the tunnels'
origin and purpose. But even among the many mysteries of the ancient
world, the Great Antrum on the Bay of Naples surely remains among the
most intriguing.

C.F. Hardie. "The Great Antrum at Baiae." Papers of the British School at Rome 37 (1969); Peter James and Nick Thorpe. Ancient Inventions. London: Michael O'Mara, 1995; A.G. McKay. Cumae and the Phlegraean Fields. Hamilton, Ont: Cromlech Press, 1972; Daniel Ogden. Magic, Witchcraft and Ghosts in the Greek and Roman Worlds: A Sourcebook. Oxford: Oxford University Press, 2002; R.F. Paget. "The 'Great Antrum' at Baiae: a Preliminary Report. Papers of the British School at Rome 35 (1967); R.F. Paget. In
the Footsteps of Orpheus: The Story of the Finding and Identifications
of the Lost Entrance to Hades, the Oracle of the Dead, the River Styx
and the Infernal Regions of the Greeks.
London: Robert Hale, 1967; H.W. Parke. Sibyls and Sibylline Prophecy in Classical Antiquity. London: Routledge, 1988; P.B. Wale. "A conversation for 'The Antrum of Initiation, Baia. Italy'." BBC h2g2, accessed 12 August 2012; Fikrut Yegul. "The Thermo-Mineral Complex at Baiae and De Balneis Puteolanis." The Art Bulletin 78:1, March 1996.

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