The relic is a circlet of woven rushes about 21 centimetres across, bound in gold thread and now kept in a crystal-and-gold reliquary; the thorns that tradition attached to it were long ago detached and dispersed as separate relics across Europe. Its recorded history begins in Constantinople, where it was among the Passion relics kept in the imperial chapel of the Pharos.
When the Latin emperors who seized the city in 1204 fell into debt, the Crown was pledged to Venetian financiers, and in 1239 King Louis IX of France redeemed it for an enormous sum. He received it barefoot at Sens and carried it into Paris, then built the Sainte-Chapelle, itself a reliquary in stone and glass, to enshrine it.
The Church venerates the Crown as a relic of the Passion while making no scientific claim about its authenticity. Transferred to Notre-Dame in 1806, it was displayed for veneration on the first Friday of each month, every Friday in Lent, and on Good Friday, carried by the Knights of the Holy Sepulchre. Since the cathedral's reopening it rests in a newly commissioned reliquary in the axial chapel.