So with Destiny adding SIVA to the game a big plot hole/mystery to me can finally be explained. We all know the Titans built the Wall but have you ever looked at that thing? It's fricken huge. I always thought that given the slippery and vague timelines we get from the lore that it would still be pretty damn difficult for something so massive to be built by early post collapse guardians. But with SIVA being a nanotech that built whole cities in days the idea of early guardians building the wall seems easier to believe. It would also explain why it seems so busted up in places because after losing thousands of guardians at Mare Imbrium on the moon the vanguard likely has a skeleton crew guarding it. This would also explain why the fallen seem to live in some segments and could be how they discover SIVA tech. If you have any thoughts or observations please leave them in the comments.