Answer:
Knight represents everyone who goes through life and searches for something ideal, and Eldorado represents those unreachable ideals.
Step-by-step explanation:
Knight represents everyone who is going through life and who is searching for someone. The journey described in the poem is life, presented as an endless search for something better and greater symbolized in the glory and gold of Eldorado.
Therefore, Eldorado itself presents some almost unreachable good, the ideals people hold and crave and search for their whole life. In this poem and everyday communication, Eldorado is used as a symbol of yearning and symbol of the promised place.
Some analyses even think Poe saw Eldorado as the symbol of death – it is the place which knight can reach only after a long journey and suffering. This analysis is explained by the thought that Ideal is unreachable. In the Christian tradition, ideal doesn't exist in this world, but only in the realms of heaven, which means after death.