Keats' landscape for this poem is as varied and dynamic as his imagination will allow. In fact, come to think of it, it's firmly located within the speaker's own mind. Sure, nature plays a starring role in just about every line of the poem, but when you get right down to it, nature doesn't appear in descriptive terms. Keats isn't wandering around amidst rocks, trees, and babbling brooks. Nope, when you look closely, you'll see that items from nature are most commonly used as vehicles in metaphors about the speaker's own emotional state. His ambition grows as he imagines his future books as storehouses of grain; his love becomes a version of the night sky.
Come to think of it, most of Keats's setting can be summed in one little phrase: "It's all about me." It's ironic, really, since the entire movement of the poem is an attempt to get away from all of his personal passions and desires.
When the speaker finally does get outside his own head, he does so in a rather remarkable way: he moves out to "the shores of the wide world" (line 12). We're not quite sure where to put that on a map, but we're guessing that it's a few steps away from reality – or at the very least, up in a spaceship. Since space travel wasn't exactly common practice in the 19th century, we're left with a sneaking suspicion that Keats intends to make his ultimate location rather unimaginable. So, from nature-as-metaphor to nature-as-uncharted waters, Keats' poem is one long trek through a very, very strange terrain: the poet's own mind.