Why would Catalonia and Occitania be one province? The Pyrenees mountains make for a pretty strong natural border. Catalonia doesn't trace back to ancient Rome but the middle ages. It's one of the medieval Christian kingdoms that fought with the various Islamic regimes that ruled southern Spain until it was subsumed into Aragon (which was later merged with Castile.) Prior to that they were all part of a unified Visigothic empire.