Ishmael writes below that -

>The Roman road makes a sharp turn before Silbury hill. If it went beneath then Silbury could not be neolithic.<

Yes, quite, and I think it's worth mentioning that Adams Grave, Wansdyke and Piggledean are all some way <i>outside</i> Avebury Village (though I guess you might just about allow Waden Hill in).

>Sambourne, which comes from the celtic, as does Kennet, comes from sumina, which may have meant water.<

Forgive my ignorance, but was is 'sumina'? I'm also not sure what you mean by the word 'Kennet' being 'Celtic' nor your understanding of the origin of the word Kennet to mean 'water'. My own understanding of the etymology of the word 'Kennet' is something quite different (though I'd be happy to learn of alternative theories :-)