The poem is set both inside and outside a forest. We'll explain. At the beginning of the poem, the speaker peers into the woods from outside and tells the nightingale, "Whoa, dude, I'm jealous that you get to live in there. How can I get a place like that?" He imagines that the bird is living it up in the forest like a pleasure-seeker in the sun-soaked Mediterranean. When he compares the forest to the world outside, the place where most humans live, it makes the outside world look like the site of endless death and decay. Talk about a skewed perspective! He ignores all the good parts of the human world.
Then the giant bird of Poetry comes along to drop the speaker smack into the middle of the forest at night: the nightingale's home! The thick foliage blocks the light from the moon and the stars and creates a pleasant smell of many different plants. Through this whole scene, he continues to hear the heartbreaking song of the nightingale. Then his imagination takes him back through time, and he experiences the nightingale through others who might have heard the same song. But just as quickly as he left the regular world, he returns to it again. Once again the forest seems like a desired but inaccessible place as the nightingale flies away to find a new perch in the next valley.