A Cathedral Built to Rank Beside a Royal Relic

Notre-Dame's construction, begun in 1163 under Bishop Maurice de Sully and continuing for close to two centuries, made it one of the most ambitious Gothic buildings of its age, but its role as custodian of major Passion relics came slightly later and through a specific royal transaction rather than through the cathedral's own foundation. King Louis IX, later canonised as Saint Louis, purchased the Crown of Thorns from Baldwin II, the financially desperate Latin emperor of Constantinople, in 1238 to 1239, paying a vast sum to redeem it from Venetian creditors to whom Baldwin had pawned it.

Louis judged the relic too important for the cathedral alone and built the Sainte-Chapelle, a purpose-made royal reliquary chapel within the royal palace on the same island, specifically to house the Crown and the other Passion relics he acquired in the same years. The Crown of Thorns moved to Notre-Dame only later, after the Sainte-Chapelle lost its royal function following the French Revolution; the cathedral has held it since the nineteenth century as the closest surviving major ecclesiastical building to its original royal chapel, displaying it on Fridays in Lent and on Good Friday rather than continuously.