Hercules and Cacus: A Monster in the Cave
Evander’s Tale: Setting the Scene
In Book 8 of Virgil’s epic poem the Aeneid, the Trojan hero Aeneas visits king Evander, whose small settlement stands on the future site of Rome. Evander is celebrating an annual festival in honour of Hercules, and while the feast continues he tells Aeneas the story of why his people honour this hero above every other god.
Evander’s story is an aetiological myth — it explains why the Romans built the Ara Maxima, the Greatest Altar, in the Forum Boarium and worshipped Hercules there centuries before Rome itself existed.
The Monster in the Cave
Evander points to a crag on the Aventine Hill and describes the cave that once stood there. He calls the creature inside the semihominis Caci facies — the half-human form of Cacus — and says Volcanus erat pater — Vulcan was his father, the god of fire and metalworking. Cacus breathes black fire, described as ore vomens ignes — vomiting fires from his mouth — as he moves his huge bulk around the mountainside.
Virgil makes the horror vivid before the fight even starts. On Cacus’s doorposts hang the pale, decaying faces of his past victims, and the ground outside is always warm with fresh blood. This gruesome detail tells the reader exactly what kind of monster deserves to be destroyed.
Cacus’s crime is theft. While Hercules rests nearby with cattle won from defeating the monster Geryon, Cacus steals four outstanding bulls and four heifers. He drags them cauda in speluncam — by the tail into the cave — so their footprints point the wrong way and cannot be tracked back to his lair.
Cacus’s trick almost works — there are no tracks leading anyone to the cave. But as Hercules prepares to move on with the surviving herd, one of the hidden cows lows from deep inside the cave and answers the calls of the herd outside. Virgil says she Caci spem … fefellit — frustrated Cacus’s hope — giving away the hiding place with a single sound and triggering the fight that follows.
The Fight: Hercules Breaks Open the Cave
Furious, Hercules grabs his knotted club and races up the mountain. For the first time in the story, Cacus is afraid: he shuts himself inside and drops a huge boulder, held by chains, across the entrance. When Hercules cannot force his way through the sealed doorway, he tears the whole rocky peak from the mountainside and hurls it aside. Virgil compares the sight of the exposed cave to the underworld itself being suddenly uncovered to the light — an extended comparison that makes Hercules’s feat of strength seem almost more than human.
Trapped, Cacus breathes out a blinding cloud of black smoke to cover his escape. Virgil writes non tulit Alcides animis — Hercules did not endure this in his fury — and leaps straight through the flames. He seizes Cacus and strangles him, described starkly as leaving him with elisos oculos et siccum sanguine guttur — his eyes forced from their sockets and his throat drained of blood. The doors are wrenched off, the stolen cattle are dragged into the light, and Cacus’s shapeless corpse is pulled out by the feet.
After the killing, Evander says the Ara Maxima was founded in Hercules’s honour, with Potitius as its first founder and priest and the house of Pinarii as guardians of Hercules’s sacred rites. Priests called the Salii sing a hymn listing Hercules’s feats and welcoming him to the celebration — the story ends by explaining a real Roman religious practice.
How Virgil Tells the Story: Verse Techniques
Virgil writes in dactylic hexameter, the traditional metre of epic poetry. He often shifts into the historic present tense to speed up the action, switching to present-tense verbs such as rapit — he seizes — at the exact moment Hercules grabs his weapons, even though the events happened long ago.
Virgil also repeats words for emphasis, a device called anaphora. When Hercules searches for a way into the sealed cave, Virgil writes ter … ter … ter — three times … three times … three times — to show his mounting frustration before he gives up trying the doorway and tears open the mountainside instead.
The underworld comparison in the cave-opening scene is an extended simile, borrowed from Homer, which exaggerates both the size of Cacus’s lair and the scale of Hercules’s achievement. Later, when the Salii priests sing Hercules’s praises, Virgil uses apostrophe, switching to direct speech that addresses Hercules himself directly, as though the hero is listening to the hymn.
Watch out for perfect passive participles such as elisos (forced out) and raptos (seized). They describe something already done to the noun before the main action of the sentence, not something happening in the present — reading them as active or present-tense changes the meaning of the sentence, so it is worth checking the ending and voice before you translate or comment on them.
Why the Story Matters
Evander’s story does more than entertain a guest. It shows Aeneas that this land has already produced heroes and altars sacred to the gods, giving him confidence that Italy is the right place to found his new city. The tale also lets Virgil connect the age of Hercules directly to Augustus’s Rome: the same Ara Maxima that Hercules earned by killing Cacus still stood in the Forum Boarium in Virgil’s own lifetime, linking myth to the streets his readers actually walked.