Having survived the depths of Hell, Dante and Virgil ascend out of the undergloom to the Mountain of Purgatory on the far side of the world. The Mountain is on an island, the only land in the Southern Hemisphere, created by the displacement of rock which resulted when Satan's fall created Hell (which Dante portrays as existing underneath Jerusalem). The mountain has seven terraces, corresponding to the seven deadly sins or "seven roots of sinfulness." The classification of sin here is more psychological than that of the "Inferno", being based on motives, rather than actions. It is also drawn primarily from Christian theology, rather than from classical sources. However, Dante's illustrative examples of sin and virtue draw on classical sources as well as on the Bible and on contemporary events.