Although Johnson is better known as a prose writer than a poet, we can distinguish his famous poems quite easily. His two most famous poems—"London" and "The Vanity of Human Wishes"— are both imitations of satires by the Latin poet Juvenal.
And how do we know they're imitations of Juvenal's satires? Easy: their subtitles tell us so. The subtitle of"London" is an "Imitation of the Third Satire of Juvenal." And the subtitle of "The Vanity of Human Wishes," is, of course, "The Tenth Satire of Juvenal Imitated."