Amiens Cathedral, interior of north west portal

This view reveals the secret of Robert of Luzarches's design for the western towers. Very shallow in their east-west projection they sit atop massive masonry bridges cunningly built into the interior and exterior of the western frontispiece. Here you see the interior portion of the northern bridge, a pointed barrel vault immediately above the unusual window which has the form of a spherical triangle. Zoom in on the masonry above the doorway--you can see a lot of alarming cracks. The cracks are evidence that the structural system was not perfect: it has settled to the north necessitating the addition of a great buttress installed c.1380.