I think it is a reference to the game Last Remnant (we also got haircuts from that game, just saying).
As for what exactly it is here... I kind of figured it was the "last remnant" of a floating island. Lets say the Zeta Quadrant used to stand there, but now the only remnant is what we see.
Eureka was historically where the ultimate weapons were stored in Final Fantasy III, so a favorite theory of mine was always that in Eorzea, it was where the Allag stored their Ultima Weapons. I think Azys Lla and Seal Rock are where much of Allagan R&D went on, though.
