Complex sentence: The remaining 20% of the province is the Loire-Atlantique department which now lies inside the Pays de la Loire region, whose capital, Nantes, was the historical capital of the Duchy of Brittany.
Split into simpler sentences: The remaining 20% of the province is the Loire-Atlantique department which now lies inside the Pays de la Loire region. Its capital, Nantes, was the historical capital of the Duchy of Brittany.