It’s impossible to put ourselves into the minds of those who built the last phase of Silbury but I can’t believe that they wouldn’t have used the flat top for something (hence I’ve always thought it was flat). Dunno though. It is a very beautiful thing when seen from a distance – almost the further you go the better – and I don’t think that was unintentional.
I’d still say to anyone who hasn’t climbed Silbury – don’t do it. Not on this thread because of conservation concerns but because you will have ‘conquered’ it, and you’ll never feel the same way about it again.