The threefold division of the Purgatorio, marked only by more elaborate preludes, or by a natural pause in the action of the poem, is⁠—1. From Canto I to Canto IX ; 2. From Canto IX to Canto XXVIII ; 3. From Canto XXVIII to the end. The first of these divisions describes the region lying outside the gate of Purgatory; the second, the Seven Circles of the mountain; and the third, the Terrestrial Paradise on its summit.