 The timber beams under the roof were replaced with an iron framework covered with copper plates

The cathedral has three great portals or entrances, opening into the nave from the west and into the transepts from north and south.The portals are richly decorated with sculptures, which rendered biblical stories and theological ideas visible for both the educated clergy and lay-folk who may not have had access to textual learning.Each of the three portals on the west facade (made 1145-55) focuses on a different aspect of Christ's role in the world; on the right, his earthly Incarnation, on the left, his Ascension or his existence before his Incarnation (the era "ante legem"), and, in the centre, his Second Coming, initiating the End of Time.