Where It All Goes Down
The setting of this poem is… well, the entire world. Yup, the speaker says it in the first couple of lines of the poem: "Let observation, with extensive view/ Survey mankind from China to Peru" (1-2). So the poem literally covers a lot of territory—all the way from Far East Asia to South America, with everything in between.
Not only does the speaker cover mankind all over the world, he also covers a huge chunk of human history. He goes all the way back to the ancient Greeks and Romans, as when he says: "Such bribes the rapid Greek o'er Asia whirl'd;/ For such the steady Romans shook the world" (179-180). Then he brings everything up to modern times (as in, the eighteenth century). Our speaker's out to show that all, and we do mean all, of humanity's striving—past, present, near, or far—is ultimately doomed, which is why we need to turn to God. The sheer size of the setting for this poem just adds further proof for his argument.