For centuries, the Sedan castle was both a luxurious princely residence and a fortress considered to be impregnable. Its gigantism and the thickness of its walls still testify of the role formerly played by the princes of Sedan on the French and European political scenes. Built in 1424 and occupying a 2.47 acres (10,000 m²) surface in the middle of the 16th century, the castle held a strategic location between France and the Holy Roman Empire. The city of Sedan remained a principality for more than a century before merging with the Kingdom of France in 1642.