One of the best things about studying classic literature is that the themes found therein apply as much today as they did at the time o writing. So it is with Yeats's The Lake Isle of Innisfree, a short but magnificent little narrative exploring the need many people feel to escape modern life and/or city life, and retreat to a place of solitude and quiet. The poem is heavily influenced by American writer Henry David Thoreau, who retreated to Walden Pond for a couple of years in the mid-1800's to do just what Yeats speaks of. Yeats envisions a cabin for himself, a place where he will hear water murmuring against the shoreline and not much else--sounds and images he imagines as he stands in the city on the concrete pavement.
the main theme is nature
it talks about the splendour of nature, man's loathness towards modern, polluted city, his admiration towards the lake and his yearning to go back and live there, tranqulity, peacefullness and freshness in nature etc.