The Chateau in Nantes was built by François II, the last Duke of Brittany, in the 14C in order to defend Brittany – from the French!
He was succeeded by his daughter, the Duchess Anne who was forced to marry two French kings resulting eventually, after her death, in the union of Brittany with France in 1532. The Chateau retained its importance, however, because it became the Breton residence of the Kings of France. And it was here, in 1598, that Henri IV signed the Edict of Nantes, giving religious freedom to the Protestants.
The Chateau changed over the centuries, with new buildings, an explosion which destroyed one section, and change of use. Even the path of the River Loire in Nantes has been changed with the building of an embankment and changes to the course of the Rivers Loire and Erdre (1926-46) – originally the Loire lapped against these walls of the chateau.

Inside the walls the original buildings are splendid in white limestone, with ornately carved window surrounds
An interesting museum allows you to see inside these buildings and explains the development of Nantes over the centuries, particularly the shipping trade.
Outside the walls Duchess Anne looks proudly at her castle.
Further information
The walls of Nantes, and its history – very interesting blogsite
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