What point within the nearby metropolis/town/... are the distances and bearings given by locate city referenced to? Is it the center of the town square, perhaps? A geometric center-of-population-mass? Some other sort of computed centroid?
Whatever the DM says it is
For some inconceivable reason, the spell's authors didn't rely on the spell being used as a non-narrative navigational aide. Absolutely no mention is made to it's capabilities as a nuke nor to how "population" or "town" is assessed.
This problem, therefore, falls squarely in the DM's prerogative, and the specific details of the spell's instantiation are a function of the game's narrative.