The nave of Rouen Cathedral displays primitive Gothic architecture. Its 11 bays, almost all equal, are lined with central pillars wrapped in single-ply columns to reinforce the vertical impression towards the ribbed vaults of the ceiling. The arcades are superimposed on four floors on each side. The gallery bays between the large arcades and the triforium are typical of the great cathedrals of the second half of the 12th century (Noyon, Laon, and Notre-Dame de Paris).