If you're not out shooting things in Destiny, chances are you're in the Tower, jumping from potted plant to potted plant while you wait for your team to get ready. We know that the Tower is located in "the last city" on Earth, but where is that, exactly?
One clever Destiny player seems to have hit upon an answer. In an enjoyable Reddit post (thanks, Zee), sundial enthusiast dwntwn_dine_ent_dist has used the position of the in-game sun—after determining that the day in question is an equinox—to figure out Tower's geographic location.
Shadows of vertical objects cast on the level ground by the sun move counterclockwise. From this, it must be that the Tower (and the City) are in the southern hemisphere. This is consistent with the name "North Tower", which is roughly the northwest part of the Tower overall. (True north is roughly the direction you would walk from Rahool to Xander 99-40.)
On an equinox, an observer's latitude is 90 degrees minus the altitude of the sun at local noon. The screenshot shows a shadow cast by a tall object at noon, as viewed directly from the side. It shows a latitude of about 29°.
There are three places where there is land at 29° south:
2) South Africa/Lesotho
Only one of those options has the mountains that can be clearly viewed from the tower, meaning that, according to the sun's position, the Tower is located somewhere in South America, nestled in the Andes mountains.
Of course, that's all assuming that Bungie didn't just pick the sun's position at random, and that someone made a conscious decision to put the Tower in a specific location and not just in "a cool-looking place with mountains." But hey, the Tower's gotta be somewhere, right? Might as well be there.