A gallant knight sets out, in sunshine and in shadow, singing, to seek Eldorado, the land of gold. But the years pass, a shadow falls over his heart, and he finds no land that looks like it. Old now and failing, he meets a pilgrim shadow and asks where Eldorado is.
The answer closes the poem and opens it at once: ride «over the Mountains of the Moon, down the Valley of the Shadow», if you seek Eldorado. Which is to say: it is not in this world. Poe wrote these lines in the year of his death, and they are at once an adventure poem and an allegory of every quest that ends, perhaps, only on the far side of life.