 The inner circumference of the crown is approximately 58 centimeters and it weighs about 2 kilograms.The surviving French Crown Jewels and main Regalia including a set of historic crowns are principally on display in the Galerie d'Apollon of the Louvre, France's premier museum and former royal palace, and scattered in different museums like the National Library of France, the Basilica of Saint Denis the Natural history museum, the École des Mines or in Reims.The Dukes of Brittany were crowned with a royal crown said to be that of the former kings of Brittany in a ceremony designed to emphasise the royal ancestry and sovereignty of the reigning duke.