The central tympanum depicts not the Last Judgment, but the preaching of the Good News. Christ is thus seated as a teacher rather than as a judge. Surrounding Him are the apostles, who have received instructions to teach the whole world, while the lintel and nearest arch portray the peoples - mythological and monstrous as well as real and known - who received the message. On the upper arch is found another great medieval theme: the labors of the months, interspersed with the signs of the Zodiac, which mark the passage of time.