41 At the conclusion of the central section of the Church's great Credo —the part that recounts the mystery of Christ, from his eternal birth of the Father and his temporal birth of the Virgin Mary, through his Cross and Resurrection to the second coming—we find the phrase: “he will come again in glory to judge the living and the dead”. From the earliest times, the prospect of the Judgement has influenced Christians in their daily living as a criterion by which to order their present life, as a summons to their conscience, and at the same time as hope in God's justice. Faith in Christ has never looked merely backwards or merely upwards, but always also forwards to the hour of justice that the Lord repeatedly proclaimed. This looking ahead has given Christianity its importance for the present moment. In the arrangement of Christian sacred buildings, which were intended to make visible the historic and cosmic breadth of faith in Christ, it became customary to depict the Lord returning as a king—the symbol of hope—at the east end; while the west wall normally portrayed the Last Judgement as a symbol of our responsibility for our lives—a scene which followed and accompanied the faithful as they went out to resume their daily routine. As the iconography of the Last Judgement developed, however, more and more prominence was given to its ominous and frightening aspects, which obviously held more fascination for artists than the splendour of hope, often all too well concealed beneath the horrors.
Source: Spe Salvi (Vatican.va)