Nah, that's part of an intergalactic StarGate that was destroyed by the Go'uald! 
Maybe it's a station built by one of the groups of the missing. Seed ships and all that.
LTT 15493 , around the orbit of LTT 15493-1Where?
I wasn't thinking about the ring itself, but some other internal part.
Also it doesn't look like a station habitat ring to me either.
As said before - more of a structural element you wouldn't see from the outside. Be it station or capital ship.
Did the ships that float around the same site already exist back then?