By the power of truth, I, while living, have conquered the universe.
Posted by: ImmortalJoshua
It just seems pointless for Bungie to put that scene in there if it was just like a control or activation center for the Portal. Or just simply part of the Portal.
It's like "yea we showed them the portal in ODST, but lets have this underground part of the Portal and not say it is just so that the fans can speculate in vain"
It's where they first discovered the Portal, that's what every piece of evidence shows. Doctor Endesha continuously states that the seismic activity he read came from beneath Vergil's data center, in the Legendary Ending it turns out it's the Portal Artefact we see (along with Vergil's data center).
It's tying in ODST to Halo 3 for those who aren't quite as invested in the lore.