The labyrinth is made of inlaid stone in the floor of the cathedral.
Credit: Created by C.garciadelucas, accessed from https://commons.wikimedia.org/wiki/File:Labyrinthe_de_la_cath%C3%A9drale_de_N%C3%B4tre-Dame_de_Chartres.jpg under the Creative Commons Attribution-Share Alike 3.0 Unported license