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.