Some have supposed these secret caves and vaults to have been places of concealment of the inhabitants and their treasure, during times of war and violence; or rude temples for the performance of religious ceremonies in times of persecution. There are not wanting other, and grave writers, who give them a still darker purpose. In these caves, say they, were taught the diabolical mysteries of magic; and here were performed those infernal ceremonies and incantations, horrible in the eyes of God and man. “History,” says the worthy Don Pedro de Roxas, “is full of accounts that the magi taught and performed their magic and their superstitious rites in profound caves and secret places; because, as this art of the devil was prohibited from the very origin of Christianity, they always sought for hidden places in which to practise it.” In the time of the Moors this art, we are told, was publicly taught at their universities, the same as astronomy, philosophy, and mathematics, and at no place was it cultivated with more success than at Toledo. Hence this city has ever been darkly renowned for mystic science; insomuch that the magic art was called by the French, and by other nations, the Arte Toledana. Of all the marvels, however, of this ancient, picturesque, romantic, and necromantic city, none in modern times surpass the cave of Hercules, if we may take the account of Don Pedro de Roxas for authentic. The entrance to this cave is within the church of San Gines, situated in nearly the highest part of the city. The portal is secured by massive doors, opening within the walls of the church, but which are kept rigorously closed. The cavern extends under the city and beneath the bed of the Tagus to the distance of three leagues beyond. It is, in some places, of rare architecture, built of small stones curiously wrought, and supported by columns and arches. In the year 1546 an account of this cavern was given to the archbishop and cardinal Don Juan Martinez Siliceo, who, desirous of examining it, ordered the entrance to be cleaned. A number of persons furnished with provisions, lanterns, and cords, then went in, and having proceeded about half a league, came to a place where there was a kind of chapel or temple, having a table or altar, with several statues of bronze in niches or on pedestals.