sentences:  This gave the ambulatory a striking openness, light, and greater height.The builders then constructed the nave of the church, also using rib vaults.It was constructed in four levels; the arcades on the ground floor whose two rows of columns received the ribs of the ceiling vaults; the tribune above it, a gallery which concealed the massive contreforts or buttresses which pressed against the walls; the triforium, another, narrower gallery; and, just below the ceiling, the "claire-voie" or clerestorey, where the windows were located.