Every part of the Gothic cathedral had metaphoric significance. So it is reasonable to think that the summit of the less-photographed northern spire of Notre Dame was intended to represent the crown of thorns as an element of the Passion.

Exposure data: 105mm, 1/250 of a second at f/8 and ISO 200, hand held; processed in Adobe Camera RAW and Photoshop, selective focus added in FocalPoint, converted to monochrome using Photoshop.
See also: iPhonographie de Paris.