Mexico City is not a particularly tall city; the urban canyons of downtown New York or Boston do not exist here. Indeed, it's rather low-lying nature creates the insular neighborhood pockets that can make it possible to ignore the bustling sprawl that encircles you.
Except you can't see the sky.
Sure, I have seen stars and sunsets here, and dramatic creeping thunderheads. But never fully - the view is obstructed by buildings, billboards, powerlines. During a week when others were up in the mountains, the feeling of being somewhat boxed in was acute.