Castles in general have a strong beginning in France. The first were called donjons - or towers, and had a simple design that gave them an advantage against attackers. Slowly more massive fortifications started to appear throughout France and Normandy.
Wiliam the Conqueror's influence in castle building is undeniable. He had a castle in Caen, Normandy and more English castles. French castles then began a long transition from being defensive strongholds to mini palaces. This occurred because of new political divisions.
Some people call France the "Country of Castles", because there's so many of them.
Foix Castle - The Foix castle has been slowly repaired and it now serves as a museum. However, a thousand years ago it was one of the mightiest castles of the world.
Vincennes Castle - Formidable castle located in the Ile de France. One of the oldest and most impressing fortresses.