In the 1200s, the cathedral stood in the heart of the canonical district, which occupied a quarter of the old Gallo-Roman city. It was a real city within a city, with a bishop’s palace, churches, canon houses, a library, a school, a prison, even a hospital, and all of which are no longer in existence.
From the original Romanesque construction in the 12th century, only the crypt and the base of the north transept tower (1) remain. Following a fire in 1138, the north transept (2) was rebuilt.
During the years that followed, the nave was reconstructed in a Gothic style and the south arm of the transept (3) was completed in 1215.