the crypt or mystery-place leads us to something below the Christian Weltanschauung, something older than Christianity, like the pagan well below the cathedral at Chartres, or like an antique cave inhabited by a serpent
Jung defines the crypt as an archaeological and psychological stratum beneath conscious Christianity, signifying pre-Christian initiatory space where death and rebirth are enacted.
, Collected Works Volume 18: The Symbolic Life, 1976thesis