I'm reposting this from a thread I started waaay back in September of last year. I think it's time
TITLE: The chance to find some REALLY crazy stuff out in the galaxy!
BODY: By crazy, I was thinking of immense constructs that scientists have only theorized about, such as:
-Dyson spheres/swarms/bubbles/rings/etc.
-Ringworlds, or Niven rings, if you will (like in Halo, to use a probably-not-at-all-scientific example, but that doesn't mean it'd be impossible to make one for some species or group of species, be they extinct or extant, high up on the Kardashev scale)
-Artificial stellar bodies (the Death Star comes to mind as an example, but the purpose and size don't need to match those of the Death Star)
-matrioshka or Jupiter brains
-space fountains and elevators
-Launch loops...
The list could go on for a while. Basically, it's anything described on this wikipedia page (and probably more!): en.wikipedia.org/wiki/Megastructure
The great thing is, the species that created something like one of these things wouldn't necessarily need to still be around. They could have died off, transcended corporeal form, what have you. But something like one of these insanely massive, complex structures could still live on. Or, maybe it's falling apart, but there's still enough intact to figure out what it once was. Or maybe we can't figure it out! Indiana Jones, eat your heart out
Now, before everyone starts with the harumphs, I understand the odds of finding something like one of these is (probably) insanely, ridiculously small. Perhaps they don't exist, at least not in our galaxy. Still.. maybe throw one of each into the game, somewhere, for us to find.
Maybe one of us, one day, will find one

And in game terms, it'd be like winning the biggest lottery you could ever dream of. The factions would offer you the moon and stars for information about such a wonder (or maybe just a moon, a small one...

). I know the prospect of something like that being out there would be tremendously appealing and compelling, regardless of the (actually!) astronomical odds of actually finding something.