Where on the planet do you think the tower is located? Given that we start out in Russia and fly on what I believe was meant to be a long trip, it could be almost anywhere. Obviously, there is a huge mountain chain so that rules out a lot of places.
I don't recall seeing the aurora from the tower so that eliminates the far northern and southern regions.
There aren't enough people present in the tower to determine through accent. I believe at this point in the future there is more of a world culture anyway.
My guess puts it somewhere in the Apls. Possibly Italy.
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I'm guessing somewhere in the Cascade Range in Washington. If it existed, Bungie could probably see it from their window.