Dr Paget and Mr Jones knew of two tunnels cut through the crater wall at the site of the Roman dockyard. One of them was named the Grotto della Sibilla and its custodian: Signor Alessandro maintained that it was in fact the original entrance to the Underworld. But they both went on to explore much further and deeper, following tunnels too narrow to turn around in, and in fear of being overwhelmed by noxious gases, convinced that they had found the argillae of the Cimmerians.
For Homer's Odyssey describes the Cimmerians as living beyond the Oceanus, in a land of fog and darkness, at the edge of the world and the entrance of Hades.
Quoting Strabo (who is quoting Ephorus) and talking about Cuma close to Avernus:
There is here a spring of water, near to the sea, fit for drinking, from which, however, every one abstained, as they thought it water from Styx. They thought, likewise, that the oracle of the dead was situated somewhere here. Ephorus, peopling the place with Kimmerii, tells us that they dwell in underground habitations, and that these communicate with one another by means of certain subterranean passages; and that they conduct strangers through them to the oracle, which is built far below the surface of the earth. They lived in the mines together, with the profits accruing from the oracle and grants made to them by the king. It was a traditional custom for the servants of the oracle never to behold the sun, and only to quit their caverns at night. At last, however, these men were exterminated by one of the kings, the oracle having deceived him; but the oracle is still in existence, though removed to another place. Such were the myths related by our ancestors.'Unfortunately, neither Strabo nor Ephorus explain what people did once they entered the Underworld. Pausanius (second century AD) goes further, but he too respects the rule of secrecy the oracles demanded.
Pausanius describes his visit to Labadeia:
Pausanias, Description of Greece 9. 39. 3 ff (trans. Jones) (Greek travelogue C2nd A.D:After Dr Paget and Mr Jones's work, Oracles of the Dead have become tourist destinations, as we no longer fear 'Necromancy' as did the Romans who had laws against 'witchcraft' and closed the oracle...
"The most famous things in the grove [at Lebadeia, Boiotia] are a temple and image of Trophonios; the image made by Praxiteles, is after the likeness of Asklepios . . . If you go up to the oracle, and thence onwards up the mountain, you come to what is called Kore’s Hunting . . . What happens at the oracle is as follows. When a man has made up his mind to descend to the oracle of Trophonios, he first lodges in a certain building for an appointed number of days, this being sacred to the Daimonos Agathon (Good Daimon) and to Tykhe (Fortune). While he lodges there, among other regulations for purity he abstains from hot baths, bathing only in the river Herkyna. Meat he has in plenty from the sacrifices, for he who descends sacrifices to Trophonios himself and to the children of Trophonios, to Apollon also and Kronos, to Zeus surnamed King, to Hera Charioteer, and to Demeter whom they surname Europa and say was the nurse of Trophonios.
At each sacrifice a diviner is present, who looks into the entrails of the victim, and after an inspection prophesies to the person descending whether Trophonios will give him a kind and gracious reception. The entrails of the other victims do not declare the mind of Trophonios as much as a ram, which each inquirer sacrifices over a pit on the night he descends, calling upon Agamedes. Even though the previous sacrifices have appeared propitious, no account is taken of them unless the entrails of this ram indicate the same; but if they agree, then the inquirer descends in good hope.
The procedure of the descent is this. First, during the night he is taken to the river Herkyna by two boys of the citizens about thirteen years old, named Hermai, who after taking him there anoint him with oil and wash him. It is these who wash the descender, and do all the other necessary services as his attendant boys. After this he is taken by the priests, not at once to the oracle, but to fountains of water very near to each other. Here he must drink water called the water of Lethe, that he may forget all that he has been thinking of hitherto, and afterwards he drinks of another water, the water of Mnemosyne (Memory), which causes him to remember what he sees after his descent.
After looking at the image which they say was made by Daidalos (it is not shown by the priests save to such as are going to visit Trophonios), having seen it, worshipped it and prayed, he proceeds to the oracle, dressed in a linen tunic, with ribbons girding it, and wearing the boots of the country.
The oracle is on the mountain, beyond the grove.
Round it is a circular basement of white marble, the circumference of which is about that of the smallest threshing-floor, while its height is just short of two cubits.
On the basement stand spikes, which, like the cross-bars holding them together, are of bronze, while through them has been made a double door.
Within the enclosure is a chasm in the earth, not natural, but artificially constructed after the most accurate masonry. The shape of this structure is like that of a bread-oven. Its breadth across is the middle one might conjecture to be about four cubits, and its depth also could not be estimated to extend to more than eight cubits. They have made no way of descent to the bottom, but when a man comes to Trophonios, they bring him a narrow, light ladder. After going down he finds a hole between the floor and the structure. Its breadth appeared to be two spans, and its height one span. The descender lies with his back on the ground, holding barley-cakes kneaded with honey, thrusts his feet into the hold and himself follows, trying hard to get his knees into the hole. After his knees the rest of his body is at once swiftly drawn in, just as the largest and most rapid river will catch a man in its eddy and carry him under. After this those who have entered the shrine learns the future, not in one and the same way in all cases, but by sight sometimes and at other times by hearing. The return upwards is by the same mouth, the feet darting out first. They say that no one who has made the descent has been killed, save only one of the bodyguard of Demetrios. But they declare that he performed none of the usual rites in the sanctuary, and he descended not to consult the god but in the hope of stealing gold and silver from the shrine. It is said the body of this man appeared in a different place, and was not cast out at the sacred mouth...After his ascent from Trophonios the inquirer is again taken in hand by the priests, who set him upon a chair called the chair of Mnemosyne (Memory), which stands not far from the shrine, and they ask of him, when seated there, all he has seen or learned. After gaining this information they then entrust him to his relatives. These lift him, paralysed with terror and unconscious both of himself and of his surroundings, and carry him to the building where he lodged before with Tykhe (Fortune) and the Daimon Agathos (Good Spirit). Afterwards, however, he will recover all his faculties, and the power to laugh will return to him. What I write is not hearsay; I have myself inquired of Trophonios and seen other inquirers.
Those who have descended into the shrine of Trophonios are obliged to dedicate a tablet on which is written all that each has heard or seen...This oracle was once unknown to the Boiotians, but they learned of it the following way. As there had been no rain for a year and more, they sent to Delphoi envoys from each city. These asked for a cure for the drought, and were bidden by the Pythia to go to Trophonios at Lebadeia and to discover the remedy from him. Coming to Lebadeia they could not find the oracle. Thereupon Saon, one of the envoys from the city Akraiphnion and the oldest of all the envoys, saw a swarm of bees. It occurred to him to follow himself wheresoever the bees turned. At once he saw the bees flying into the ground here, and he went with them into the oracle. It is said that Trophonios taught this Saon the customary ritual, and all the observances kept at the oracle. Of all the works of Daidalos there are these two in Boiotia, a Herakles in Thebes and the Trophonios at Lebadeia."