Its grandeur and complexity rivaled the greatest creations of the Protheans-themass relays and the Citadel.

The underlying scientific theory behind the creation of mass relays was still beyond the scope of humanity's top experts.

We want to send them on two- to five-year journeys into uncharted regions of space or through unexplored mass relays.

Take the mass relays.

And with several dozen mass relays in the vicinity, reinforcements from virtually every region of the galaxy were only minutes away.

Files could be transported by courier drones, unmanned ships programmed to travel through the mass relays network by the most direct routes possible.

But it wasn't just its size that made it so amazing: like the mass relays, the Citadel had originally been created by the Protheans.

Virtually all traces of the Protheans had been wiped out; only the mass relays and Citadel survived, the enduring legacy of a once great people.