Yeats imagines Innisfree as an idyllic place of peace and solitude. He imagines a "small cabin" of "clay and wattles" where he will support himself on beans and honey from his bee hive, and he will "live alone in the bee-loud glade." There is also a sense that the "peace" he will find there is connected to its natural beauty, since peace "comes dropping slow, / Dropping from the veils of the morning to where the cricket sings."
Of course, there is also the sense that this is perhaps not a real place, or that his imaginary conception of his life there is (knowingly) impractical or impossible. He hears the lapping water of the lake "always" while he is standing "on the roadway, or on pavements grey." In other words, Yeats's real world is a world of "pavements," a place where nature has been changed by man to make it easier to drive or conduct business. The contrast with the lake isle is stark: he feels a longing for this place of peace in his "heart's core," which could mean that he is longing for an ideal or feeling rather than an actual clay cabin.