Nov 26, 2022 I Brent Swancer

Mysterious Portals to Hell and the Underworld in Ancient Rome

Since the dawn of mankind and its numerous religions, there have been many that feature some form of Hell or underworld, typically portrayed as a place of eternal punishment, torment, suffering, and despair, but depending on the culture and religion can also be an intermediary period between incarnations or simply a dreary land of the dead. The various versions of Hell can be another dimension or plane of existence, or an actual place in our own physical reality located deep in the bowels of the earth. While there is much debate on whether any of the many incarnations of Hell or some sort of underworld is a literal place, there have always been persistent stories that it not only exists in some form, but that it can also be accessed from the land of the living via tunnels, gateways, doorways, or portals. Here we will look at various mysterious locations during the time of the Roman Empire that, despite being just plain creepy, are said to be actual entrances to Hell itself.

There is a place on the northern shore of the Bay of Naples that has long been steeped in history, mystery, myth, and magic. Known as the Phlegræan Fields, it is a desolate place; a barren wasteland strewn with rubble and intersected by deep underground vents that belch out choking fumes and fire. Legends and strange phenomena cling to this hellish, smoke-wreathed landscape, so it is perhaps no wonder that these fields are a location believed since ancient times to hold a tunnel that leads to Hell itself. The Phlegræan Fields is a plateau that is part of an ancient volcanic caldera not far from Mt. Vesuvius, the volcano known for laying waste to the once great city of Pompeii. The heavily volcanic area, which is pitted with steaming vents, sulphur spewing crevasses, and even flaming holes in the ground, was well-known in Greek and Roman myth and is heavily associated with stories of magic and prophecy.

One of the greatest legends originating from here is that of the Cumæan sibyl, or prophetess, that was featured in Virgil's epic the Aeneid, which tells of the hero Aeneas' journey through the Land of the Dead, guided by the Sibyl. This prophetess took her name from the nearby town of Cumae, itself having the legendary distinction of being one of the landing places for Daedalus, the mythical father of Icarus of lore. The Sibyl was depicted as a woman bestowed with immortality by the sun god Apollo and gifted with powers of prophecy, who was said to dwell in a cave somewhere in the Fields that also served as an entrance to the underworld. Her powers were described as vast, and Virgil liked to depict her sitting in her cave feverishly scrawling the future onto leaves. An interesting story concerning the Sybil is that she once possessed nine magical scrolls that allegedly outlined the entire future of Rome in detail, which she offered for an exorbitant sum to a Roman king by the name of Tarquinius Superbus, also known as Tarquin the Proud. When the king refused her offer, the Sybil proceeded to methodically destroy the scrolls until the king finally coughed up the vast amount of money she had demanded, and had the last remaining three sequestered away in a hidden place.

Cumæan sibyl

Although this may all seem like pure fantasy, this story is significant in that there really was a king by the name of Tarquinius and there were indeed three scrolls kept by the Greeks that came to be known as the Sibylline Books, which were thought to be the actual texts acquired by Tarquin from the Sybil. These scrolls were typically securely locked in a stone vault deep beneath a place called The Temple of Jupiter and although it is unknown if they had any real prophetic powers, the Greeks certainly thought they did, as the scrolls were said to occasionally be used to divine the future in times of imminent crisis or disaster so that such hardships could be avoided. The scrolls were considered to be of extreme importance at the time and were protected at all costs. So desperate were the Greeks to keep these scrolls that when the temple was burned down in 83 BC, envoys were allegedly sent to the far flung corners of the earth searching for any pieces or fragments that might have survived so that they could be reassembled.

It is these intriguing grains of truth inherent to this legend that have beckoned adventurous souls for centuries, who believed that there could possibly be a real cave where the Sybil resided and that it could really descend literally into the depths of Hell itself. The historically accurate features of the tale have also been cause for historians, archaeologists, folklorists, and scholars to wonder if there actually was, if perhaps not a literal opening to the underworld, then a previously unknown and unexplored cave or tunnel system that lies at the heart of the legends of the Sybil's cave. Various searches and expeditions of the Phlegræan Fields were undertaken over the years to discern the location of this mythical cave yet turned up nothing. In the face of the lack of any further physical evidence to point to a real cave or tunnel at the root of the legend, the possibility of one existing seemed more and more doubtful, and the Sybil's entrance to the underworld faded once again into mere myth.

The legend of the Cumæan sibyl's mysterious cave may well have remained shrouded in myth and legend forever if it weren't for a curious discovery made in the 1950s in the ancient Roman luxury resort town of Baiae, a place located in the western portion of the Fields that was once renowned throughout the Empire for its spas with reputed healing powers. Here, among the 2,000 year old ruins of this once flourishing and decadent resort, an Italian archaeologist by the name of Amedeo Maiuri stumbled across the entrance to a previously unknown tunnel complex, or antrum, painstakingly carved into the volcanic rock and leading down into a hill and beneath the city. The entrance itself was a plain, nondescript and narrow opening found concealed beneath 15 feet of rubble and vines behind a vineyard near the ruins of an ancient temple. This opening was unknown and obviously man made, so the excited team attempted to explore it. They did not get far. After delving only a few feet into the blackness of the narrow passage, it quickly became apparent that the place was thickly choked with potentially dangerous fumes and the heat emanating from the darkness soon became unbearable. The archaeologists abandoned their exploration of the tunnel and in the ensuing years the entrance became sort of a mysterious, forgotten curiosity.

Some years later, in the early 1960s, a British armchair archaeologist by the name of Robert Paget came across the story of this enigmatic tunnel entrance and was immediately fascinated by it. Paget just happened to be one of the few remaining people who actually entertained the idea that the Sybil's cave of legend was a real place, and so he theorized that perhaps this fume wreathed tunnel of infernal heat at Baiae was it. He quickly became obsessed with the notion, and determined to penetrate into the tunnel's mysterious depths at any cost. Gathering a colleague of his by the name of Keith Jones and a small contingent of volunteers, Paget made preparations to dare the harsh conditions of the tunnel in order to unravel its mysteries and find out just where it led to. It was to be a daunting feat that would ultimately pose more questions than answers.

From the outset it was apparent that it would not be easy going. The group was immediately greeted by pungent volcanic fumes belching from the darkness of the tunnel and they found that it was difficult to squeeze through the opening, which while measuring 8 feet high was only 21 inches wide. Once inside, the temperature proved to be uncomfortably warm, yet lured by the promise of amazing discoveries the expedition doggedly pressed ahead nevertheless. Although the passage became wider as they went, the team were able to penetrate only 400 feet into the tunnel until they came to an area made impassable due to a pile of rubble. Besides marveling at the effort and ingenuity that it must have taken ancient people to carve out such an impressive tunnel, Paget came to the conclusion that it was likely used for some sort of ritualistic purpose due to its position in relation to the entrance and its orientation with the sunrise line and therefore the solstice.

The wall of rubble prevented any further progress, but for Paget the promise of more to find was irresistible. Driven by his obsession to uncover the tunnel's secrets, Paget embarked on an ambitious project to clear the tunnel and press on. As they proceeded, it became evident to Paget and his team that the tunnel was actually only a small part of a larger, highly intricate tunnel system that would come to be known as the Antrum of Initiation, or the Great Antrum, and had been painstakingly designed for some as yet unknown purpose. All Paget could discern was that the system likely had a ritualistic nature, an idea further bolstered by clues along the way, such as numerous candle holes placed too close together to be explained by a mere need for illumination down in the stygian depths. There were also other unique design features such as evidence of double doors leading to secret passageways, jogs in the tunnels to prevent visitors from seeing the next section of the tunnel until the bend is passed, pivoting doors for closing off passages, and complicated ventilation systems, all of which added to the mystery of the tunnels. It was obvious that although the tunnel system's makers and the true purpose of this place were unknown, whoever had constructed it had undoubtedly put great effort and thought into designing it.

Perhaps the greatest mystery of the tunnels was to be found deep in the lower levels, where temperatures reached 120 degrees Fahrenheit and the air was so choked with noxious, sulfurous fumes as to be nearly un-breathable. It was here in these hellish conditions that Paget and company found a sharp bend at the end of a particularly steep passage that seemed somehow designed to prevent anyone who approached from seeing what was to be found at the end until they turned the corner. When Paget and Jones rounded that sharp bend, they were confronted with an underground stream of boiling water that they would later call The River Styx. Projecting into this super heated stream was a landing, the purpose of which could not be discerned. On the other side of the stream, another passage ascended up into an antechamber that Paget called "The Hidden Sanctuary," and continued on until a hidden staircase led up to the surface and exited at the ruins of water tanks that had once fed the Roman spas.

In the end, Paget and his team would spend nearly a decade clearing and exploring this vast tunnel system. During this time, Paget and Jones studied the mysteries they had uncovered and became convinced that the tunnel system and its boiling river were meant to be a representation of the entrance to the Greek underworld of Hades itself. After years of searching and obsessing, Paget had finally found his legendary cave of the Sybil, or at least the cave he believed the legend was based on.

To support his theory, Paget pointed to the Aeniad, and argued that Aeneas' and the Sybil's trip to the underworld bore a striking resemblance to the layout of the Great Antrum. Paget believed the course that the tunnel system took closely followed Aeneas' journey and indeed faithfully mimicked similar trips to Hades throughout Greek legend. The estimated date of the complex, around 550 B.C., is also consistent with the time the Sybil was said to have existed. Paget and Jones surmised that the intricate tunnels of the complex were meant to recreate a similar journey through the underworld and that the boiling river represented the River Styx, at which it was speculated a boatman would have once waited at the landing to take visitors across, just as in Greek legend. It was theorized that this impressively realistic depiction of Hell would be enough for the priests of the temple to convince anyone foolhardy enough to venture through its tunnels that the underworld was very real. In short, this vast, elaborate tunnel system was thought to be more or less very convincing deception to convert followers, and may have even showcased a person playing the role of the Cumæan sibyl. Paget even went so far as to suggest that Virgil himself may have been an initiate of the temple.

Paget's theories were met with a good amount of skepticism from the scientific community, which made efforts to distance itself from his wild ideas, in part because he was not a professional archeologist and also because his far out claims that he had more or less found the entrance to the underworld did not sit well with academics at the time. As a result, Paget and Jones' findings from their exploration for the better part of a decade were not even published in book form until much later, and even then with a clear disclaimer that the team's elaborate theories were not necessarily those of the academics publishing it. Regardless of the detractors and debate that raged over their ideas, Paget and Jones' work remains the most complete attempt to uncover and explore the mysteries of the complex to date.

Very little is known about the Great Antrum, and we are no closer to really understanding it than we were when its humble entrance was discovered in the 50s. There are so many perplexing questions posed by it. Who built it and why? What are the purposes of its various odd features? Why is it that visitors were not allowed to see ahead to the next section until they turned the bend? Why did the complex's activities cease and why had the passageways been blocked with rubble? How did the entrance go unnoticed for thousands of years? Did the Romans know it was there? Was it intentionally buried by the Romans and if so why? No one really knows the answers to any of these. The only mystery that does seem to have been solved was the source of the underground river's hot water, when friends of Paget's used scuba gear to explore it and found that it was fed by two vents that spewed superheated water from the volcanic Phlegræan Fields. Until the site is more deeply studied by archaeologists willing to brave its perils, it seems that the mysterious and long hidden Great Antrum of Baiae and its menacing tunnel to Hell will remain one of ancient Rome's most perplexing enigmas.

Another supposed gateway to Hell from the time of the Romans is located in the southwestern part of Turkey, in the ancient city of Hierapolis, which was founded by the Attalid kings of Pergamon at the end of the 2nd Century BC before being taken over by the Romans in 133 AD and turned into a bustling spa town. Here there is a place called the Ploutonion, dedicated to the god Pluto, also known as the god of the underworld, and it long lived up to its reputation as a purported gate to hell itself. 

The shrine was erected here after it was said that from deep within the bowels of the earth that here would erupt the breath of toxic breath of the three-headed hellhound Cerberus, and there was plenty of evidence for this to be thought to be the case. It was noticed that animals would sometimes drop dead by the entrance to the tunnel, with even birds falling from midair to sprawl out dead on the ground, and people were occasionally said to die here as well. Thinking this to be evidence of a portal to the underworld, the Ploutonion was erected at the site and pilgrims began bringing animals here to sacrifice to Pluto. The priests at the temple would then lead the animals into the temple, where they would miraculously suddenly drop to the ground dead for what seemed to be no discernible reason while the priest remained unfazed. The effect astonished both commoners and scholars alike for centuries, being seen as true evidence of the gateway’s powers, with the Greek geographer Strabo once writing:

This space is full of a vapor so misty and dense that one can scarcely see the ground. Any animal that passes inside meets instant death. I threw in sparrows and they immediately breathed their last and fell.

It remained a mystery for centuries, and it was only until recently that the mystery was finally solved. In 2013, Hardy Pfanz, a volcano biologist from Germany's University of Duisburg-Essen, travelled to the Ploutonion to get some answers, and was able to come to the conclusion that the animal deaths could be blamed on geogenic gases, that is gases given off during geological processes, and indeed he and his team found that the same volcanic vent system that fed the area’s hot springs was emitting toxic levels of carbon dioxide in the vicinity of the shrine. Pfanz would say of it:

When I read the descriptions from the ancient writers, I began wondering if there could be a scientific explanation. I wondered, could this Gate to Hell be a volcanic vent? The Plutonium shrine was constructed at the location of what was thought to be a "Gate to Hell.” We weren't sure what we would find. It could've been made up, could've been nothing. We certainly weren't expecting to get an answer so quickly. We saw dozens of dead creatures around the entrance: mice, sparrows, blackbirds, many beetles, wasps and other insects. We could see the cave’s lethal properties during the excavation. Several birds died as they tried to get close to the warm opening, instantly killed by the carbon dioxide fumes. So, we knew right away that the stories were true. Just a few minutes’ exposure to 10% carbon dioxide can kill you, so the levels here are really deadly. Almost certainly the choice of the Ploutonion's location was directly related to the seismic gas vents that exist here. Given that the underworld and the deities and myths associated with it were a significant part of their religious ethos, it makes sense that they would construct temples and shrines in places that most evoked the world that they believed lay beneath their feet. When I first recognized that the legendary breath of Cerberus is actually carbon dioxide, I was standing right in front of the archway. In that moment, I realized we had solved this ancient mystery; it was a really fantastic feeling.

As to why the priests would remain unharmed when the animals died, it was surmised that the carbon dioxide concentration changed at different times of the day and was pooling close to the floor during the rituals, where animals would get a lethal dose while the priests would stand over it and be spared. Pfanz explains of it:

We noticed that during the day, when it's warm and sunny, the carbon dioxide quickly dissipates. But because carbon dioxide is heavier than air, at night when it's cooler it pools in the arena, creating a lethal lake of gas at ground level. But it's hard to be sure if the priests really understood what was going on. Some may well have attributed their survival to the favour of the divine, while others may have regarded it as a natural – if enigmatic – phenomenon that could be observed and, at least to some extent, predicted.

Yet another ancient Roman portal to Hell lies right in the center of Rome itself at the Forum Romanum. Here lies what is known as the Lacus Curtius, or the “Lake of Curtius,” which is a mysterious pit that is said to have opened in the earth to serve as a tunnel to the underworld, appearing as a pool in the middle of the otherwise paved forum. Although the history of the Lacus Curtius is murky, one popular story was told by the Roman historian Livy, and concerns an oracle that appeared during a time of strife and foretold the fall of Rome. The mysterious oracle supposedly said that if the people of Rome did not sacrifice that which they held most dear to the underworld then their city would wither and crumble to nothing in short order, after which a chasm suddenly appeared in the earth, its dark bowels hungry for its offering. The oracle then warned that if the offering was not made to the maw of the pit, then it would devour the city itself.

The people of the city gathered around this strange pit, and all manner of valuables and treasure were thrown into it to no merely disappear into the darkness to no effect. The Lacus Curtius gathered around itself an atmosphere of fear and thick superstition, and all offerings were in vain until a young warrior horseman named Marcus Curtius, from the Curtia gens, a very old Roman Family with Sabine origins, came to the conclusion that what the pit to Hell wanted was a human sacrifice. He deduced that it was youth, courage and military might that the Romans held most dear, and so he dressed in full battle armor and sacrificed himself to the pit, after which the earth closed up and Rome was saved. After this, the pit was still said to retain magical powers, supposedly enabling one to commune with the dead. The Lacus Curtius has long since been paved over, and in modern times is no more than a rather inconspicuous circular slab of ancient stone set in the middle of the Roman Forum sealing the supposed pit, yet its keeps its mysterious history and stories and is a popular tourist attraction. It all is a rather unique and weird look into history, showing that the idea of these portals to the underworld or to Hell itself have been entrenched in the lore of some cultures. While it all seems that it must be nothing but myth and legend it certainly shines light on some oft-overlooked parts of history that most may not have ever heard of. 

Brent Swancer

Brent Swancer is an author and crypto expert living in Japan. Biology, nature, and cryptozoology still remain Brent Swancer’s first intellectual loves. He's written articles for MU and Daily Grail and has been a guest on Coast to Coast AM and Binnal of America.

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