Chartres' labyrinth is 200 m long by the way, quite a walk. Pilgrims used to walk around it on their knees... All the large cathedrals in France had one (Amiens, Reims, St. Omer, Chartres,...) but several were destroyed at the time of the Revolution.... Above is a picture of the labyrinth of St. Omer:
Interestingly enough, it was made of 2401 tiles, and guess what?
2401 = 7 x 7 x 7 x 7
Don't tell me it's a coincidence... (seven is a mighty important number in esoterica and religion) and your own body by the way.
If labyrinths weren't built by the Templars, they were made by people whom they had a close relationship with: the guilds of builders who, very often, worked under their supervision.
Labyrinths were a symbol of the quest, of the pilgrimage (the one above has clearly a cross at the center). The different twists and turns symbolized the difficulties encountered on the way (the physical and spiritual path to Jerusalem). It also represented the difficulties encountered in the alchemical path of the "Magnus Opus" (the Great Work).
The quest , spiritual path to Jerusalem, Magnus Opus, are all metaphors for finding your higher self or inner self or your spirit. Hidden within yourself with twists and turns and dark corners and endless chambers is a wondrous thing, a wondrous being of light, and that is you. Go find it.
More reading on Labyrinths