Antarctica - Russian glaciologists today measured the ancient alien latrine by sonar and said it looks remarkably like blueprints for the proposed £5 billion Thames Super Sewer.
This was first dreamed up by renowned Victorian civil engineer Sir Joseph Bazalgette - who saved London from cholera by building a huge subterranean sewerage system.
Until this weekend the inspiration behind his iconic drawings for the 21st century marvel was always assumed to be whimsy.
However this weekend's annual general meeting of the Institute for Alien Latrine Studies heard of a possible new source for Bazalgette's extraordinary brainwave.
Previously unseen diaries written by the civil engineer have suddenly surfaced and describe an iconic evening at poet Samuel Taylor Coleridge's Highgate gaf.
Number 3 The Grove is now the London des res of super model Kate Moss whose builders found the Bazalgette memoir during a recent refurb of the £8 million house.
Apparently on 5th September 1849 Bazalgette and Thomas 'The Opium Eaters' De Qunicey got totally ratrarsed on Coleridge's excellent house port and several snifters of his equally potent poppy seed paste.
Coleridge himself nine sheets to the wind then started waxing lyrical from his latest ditty Kubla Khan:
'In Xanadu did Kubla Khan a stately pleasure dome decree; Where Alph, the sacred river, ran through caverns measureless to man down to a sunless sea'...
"Mine host doth go on a bit," Bazalgette's diary entry records along with the trio's discussions of the filthy conditions endured by Londoners before the introduction of sanitation.
At some point during that evening Coleridge passed out in front of the fireplace and, the diary notes, that's when the merriment began.
'Xanadu, full of poo, always sticking to my shoe!' De Qunicey uttered in mocking jest to parody his now prostrate drugged-up host.
'Thus did Kubla Khan remark 'pon stepping on something in the dark!' Bazalgette retorted before a deep and dreamless sleep took him off to caverns measureless to man down to a sunless sea.
Quite whether any of the stoned trio actually realised that those 'caverns measureless to man' running down to a 'sunless sea' would one day be discovered under Antarctica is moot.
Bazalgette's extraordinary interpretation remains the blueprint for the Thames Super Sewer construction of which starts early next year.