: There hasn't been any megastructure in Halo since the Ark (unless you count
: the glimpse of Installation 04 at the end of Reach and the few Halo-based
: multiplayer maps).

Well, technically (and I do mean technically) the orbital tether in ODST was probably a mega-structure, though I would totally understand not wanting to count it as such.

It would likely have needed to be at least 35,000 kilometers above sea level, mostly because I don't think that there are any good ways to make a space elevator without at least reaching geostationary orbit. So you could technically fit at least a couple Requiems and/or Halos between the bottom and top of an orbital tether. Though the effect this would have on the population of Earth would be...problematic.

But yeah, you're right, no real fancy Forerunner mega-structure since Halo 3, you definitely have me on that point.

For what it's worth, I do hope we deal with Halos more in Halo 5. Maybe Jul 'Mdama will find one and take it for a spin...