What is a summary of the poem "Eldorado" by Edgar Allan Poe?

The poem "Eldorado" by Edgar Allan Poe was published in 1849. This poem was one of his last publications. This short poem is just four stanzas long, each stanza just six lines. It is about a "gallant knight" on the search for Eldorado. He searches and searches with no luck, until he meets a "pilgrim shadow" that provides him some direction. Below is a summary of each stanza.
Stanza one (rhyme scheme aabccb) introduces a "gallant knight" in search of Eldorado. The word "gallant" means brave or heroic, a fitting term for a knight. The shadow in stanza one is from the sun, suggesting an overall upbeat tone to the stanza. The knight has set out on a mission.
Stanza two (rhyme scheme aabccb) seems to create a change in the tone of the poem, suggesting the knight has grown old, a shadow cast over his heart. No spot of ground in his search has turned out to belong to Eldorado.
Stanza three (rhyme scheme aabccb) introduces a "pilgrim shadow" that the knight has come across. He asks the pilgrim shadow where Eldorado is.
Stanza four (rhyme scheme abcddc) shows the pilgrim's reply, suggesting that Eldorado may not actually be a tangible location but rather a different state of existence.
An important thing to note is the way the word "shadow" is used throughout the poem. It is used in a different manner in each stanza. First it implies a shadow from the sun, something upbeat and positive. It then moves to the shadow over the knight's heart, changing the tone of the poem. The third stanza introduces the "pilgrim shadow" who the knight seems to desperately ask the location of Eldorado. The last use of the word depicts a potential biblical reference to the valley of the shadow of death.