After repeated attempts we finally have been able to visit the "Grotto of Sybil at the edge of Lake Averno in the volcanic Campi Flegrei area near Naples.

(A flooded tunnel off an adjoining chamber)
I must confess that after several false starts we finally decided to get it together and got busy setting things up for the trip to Lake Averno. Accompanying our group was a gentleman named Carlo. He is the last descendant of the family that has for generations conducted guided tours of a fabled network of tunnels and passageways said to lead the the grotto of the Oracle Sybil a Prophetess of Greek legend.
We followed Carlo listening to his fascinating and fantastic accounts as we moved through the principal tunnels and galleries. In this first section which is of major importance we can still see ancient symbols etched on the walls (first a cross, and a palm and a bit further on a fish and more). About halfway into the exploration, on the right wall there is a small mysterious passageway that curves to the left continuing on with a long stairwell carved into the rock, ending in a flooded tunnel.
Almost at the end of the accessible portion of the gallery (the continuation is completely filled in with earth) along the right side, a stairway leads to the last room with the modest remains of frescoes and the final chamber which is completely flooded. (we perilously advanced on an improvised walkway made of wooden planks.) At this point the tour ended, at least for those who did not wish to venture into two tunnels flooded with more than three feet of water.

(Carved stairway leading to the last room)

(One of the flooded tunnels)
We will return for sure! But this time with all our gear and speleo equipment, not like Sunday tourists. Meanwhile to know more about this grotto you may visit this
link , in italian, and scroll down to see interesting survey diagrams and photos.
Here are
THE PHOTOS we snapped on this very quick visit.
And if you do speak Italian and would like to make this interesting visit yourself, Carlos's telephone number is 3336320642.