A series of cross ribbed vaults form the structure of Metz Cathedral. This system allows the opening of higher windows on the walls and roof. In the Catholic liturgy, the light symbolizes God, hence it must be able to penetrate the churches. The openings flourished in Flamboyant Gothic architecture and were hemmed with stone laces. In Saint Stephen Cathedral, a forest of thin columns, in one piece, rises to the vaults that reach a record height of 137 ft (41.41 m).