At the apse, the deambulatory with the various apse chapels, and access to the sacristy. Already used in Romanesque architecture, this was the way of allowing pilgrims and believers to worship the relics deposited in the apse chapels, and to circulate inside the church without interfering with the High Altar. The alignment with the collateral naves allows to circulate around the nave, as if it were a cloister inside the church itself. To walk is to walk without a defined direction. The work begins at the head, it is the first experience of the early Gothic (1178), (simultaneous with the Romanico) using a more sophisticated and finer structural system. The walls gradually leave their monolithic structural role of the Romanesque, becoming increasingly thinner cloths. There are 9 radiant chapels of trapezoidal plant, with broken arches as a structure, the reinforcement by outer flying buttresses, made it possible to open two floors with windows. takes place in the chancel