>>Uneducated Speculation: if the oracle at Delphi really *was* getting high on ethylene (as has been suggested fairly recently), then a hollow stone situated in the place of prophecy *might* have had a function of concentrating the fumes. So this particular universal gateway might be a cosmic bong.... <<
The stone that archaeologists think went over the vent is flat, it could, I suppose, look like a bucket bong (being biggish), but not a normal bong - in fact no, really it doesn't look like a bucket bong at all (I can't believe I am talking abount bongs!) ;-). The conical or dome-like omphalos stone, did not, I believe, go over the hole. When I was at Delphi 6 months ago the Greek archaeologist told me the omphalos stone actually decorated the top of a column with dancing nymphs around it. I have a picture of the other stone thought to have gone over the gaseous vent if you want to email me offlist.
There are lots of great articles about Delphi and the gaseous vent and a new book too - The Oracle: Ancient Delphi and the Science Behind its Lost Secrets. William J. Broad. Penguin.
Caroline Tully.