Among most peoples the primitive idea of an after life in the grave was enlarged into the conception of a common existence of the dead in the depths of the earth. The dead man does not stay confined in the narrow dwelling in which he rests; he goes down into vast caverns which extend beneath the crust of the soil we tread. These immense hollows are peopled by a multitude of shades who have left the tomb. Thus the tomb becomes the antechamber of the true dwelling of the spirits who have departed; its door is the gate of Hades itself. Through the tomb, the great company of the beings who have been plunged in the darkness of the infernal regions remains in communication with those who still sojourn in our upper world. The libations and offerings made by the survivors on the grave descend to this gloomy _hypogeum_ and there feed and rejoice those for whom they are intended. Until the time of the Roman Empire, nay, to the end of antiquity, the common man believed in this wonder.[170] To attempt to define the means by which it was brought about would be vain. These were beliefs which went back so far and were so deeply rooted in the mind of the people that men accepted them without seeking to explain them. In Rome, the idea that the spirits of the dead inhabit a common dwelling in the nether world existed from the time when the city had its beginnings. It kept in religion a coarsely naïve form which proves how archaic it was. According to a rite borrowed by the Romans from the Etruscans, a pit was dug in the centre of the city, when the latter’s foundations were laid, in order to make the _Inferi_ communicate with the upper world. First fruits and other gifts were thrown into the pit, as well as a clod of the earth of the settlers’ native country. Thus they restored their broken contact with the Manes of their ancestors. In all probability this hole was formed of a vertical pit ending in a chamber with an arched roof curved like the heaven—hence the name _mundus_ given to it. The key of the vault of this lower cellar was formed of a stone, the _lapis Manalis_, which could be raised in order to let the spirits pass. Three times a year, on the twenty-fourth of August, the fifth of October and the eighth of November, this ceremony took place: the door of hell was opened and the dead had free access to the atmosphere. These days were therefore sacred, _religiosi_, and all business was suspended on them. Recently the _mundus_ of the ancient _Roma Quadrata_ was believed to have been discovered during excavations of the Palatine, but the underground space in question is probably only a silo or a cistern. Other pits used for the cult of the dead existed elsewhere in the city. It has recently been suggested that the altar of the god Consus, which was hidden in a ditch in the middle of the Circus Maximus and uncovered during the races, was one of these mouths of hell and like that shown in representations of the funeral games of the Etruscans.[171]