According to Philostratus in his Life of Apollonius, Athanor is an occult hill surrounded by mist except on the southern side, which is clear. It has a well, which is four paces in breadth, from which an azure vapor ascends, which is drawn up by the warm sun. The bottom of the well is covered with red arsenic. Near it is a basin filled with fire from which rises a livid flame, odorless and smokeless, and never higher or lower than the edge of the basin. Also there are two black stone reservoirs, in one of which the wind is kept, and in the other the rain. In extreme drought the rain cistern is opened and clouds escape, which water the whole country.
This description should be interpreted as alchemical symbolism, since the Athanor was also the furnace supplying heat for the alchemical process. The term Athanor is also employed to denote moral and philosophical alchemy.