Complex sentence: La Défense, Paris' business district hosting the tallest buildings in the metropolitan area, spreads over the eastern part of Nanterre (the district being also divided between Courbevoie and Puteaux).
Split into simpler sentences: La Défense, the principal business district for neighboring Paris hosts the tallest buildings in the metropolitan area. It is spread over the eastern part of Nanterre (the district being also divided between Courbevoie and Puteaux).