I betcha the tower is hiding something. Just look at the banner for the Destiny forum. The area we get to run around in is tiny compared to the actual size of the Tower itself. All the Guardians have their ships stored in the tower, but there's still gotta be a lot of room available.
I'd wager there's a giant robot hidden away in the Tower. That's right. A giant robot that'll take on the Traveler or the Darkness when the time comes. What if the Traveler had a robot inside of it. Or if the Darkness has a robot. It's all starting to make sense now. I mean we saw the Mantis added to Halo, so it's only natural that we'll see mechs and giant robots in Destiny somewhere down the line. It's the natural evolution of Bungie's franchise.