This has been one of my favourite Halo mysteries ever. Funny, I was reminded of it just days ago, when reading HipiO7's thread about the Flood outbreak on Delta Halo.. I have only found three pieces of the puzzle (iirc), all in form of quotes, but they do not add up to much... This quote might give some context as of why they were buildt: [quote]Cortana: This lake couldn't have been created by volcanic action, which means it was either built this way on purpose, or was created by some other cataclysmic event. Sorry... were you trying to kill something?[/quote]It could mean that there were similar structures there before, but they were destroyed. [b]EDIT: [/b]Volcanic action: presumably how all rock based terrain on the ringworlds is made. The Forerunner build a metal scaffolding (as seen on the level Halo in 3), which is then coated with molten rock. The complete quote from the OP.[quote][i]You know, I think the Forerunners built these new structures around the old, to protect them, to honor them. Pure speculation, mind you. I'd need to make a thorough survey to be sure.[/i][/quote]If you read it carefully, you'll notice that Cortana says "new structure" and "arround the old". Which leads us to a couple of questions: which are the new and which are the old? Does she mean the regular structures we se everywhere on 05 or does she mean among these particular structurs? Worth noticing is that there are practically two types of structures, the ones made out of [i]metal[/i] and ones made of [i]stone[/i]. Some of the structures are however made out of both; a metal skeleton with stone walls, pillars, coloumns, etc. Both types do look equally odd/old/worn out, though, but could this small difference mean something? The third one is from the multiplayer map Sanctuary's description, seeing as it is located roughly in the same area and feature the same type of buildings.[quote]Whoever narrates the menus: [i]Though its original purpose has been lost to the march of eon's, this structure is now a cemetery to countless brave warriors.[/i][/quote]Whatever that means.. [b]It's been a dead end for years.[/b] I honestly don't think it'll be brought up in any form, it's probably been forgoen or ignored. Still fun to speculate though. [Edited on 10.07.2012 5:15 PM PDT]