Thanks for your comment and additional links George. I willingly admit I do not have the mathematical ability to enter into a discussion on the subject of a possible lost Mayan city - though it did make for interesting reading this morning.

Going back to Marina's website though - the page entitled 'Avebury Mechanism' is a grounded and sensible introduction to her work. Steve Marshall mentions her in the acknowledgements in his recently published book on Avebury - as he does you. And you will no doubt remember the Silbury Sun Roll :)

https://www.youtube.com/user/marinagraham