An admirable 13th Century chevet prepares the visitor for the vertiginous views of the vaults 48 metres up. This cathedral is one of the masterpieces of Gothic art in northern France. It is lit by wonderful windows that illuminate the 58-metre transept. The astronomical clock, built from 1865 to 1868 by Louis-Auguste Vérité, has 90,000 parts. 52 faces show the seasons, length of day and night, etc.