The Old Subprefecture, locally known as Ancienne Sous-Prefecture de Sedan, lies in the city of Sedan, in the Ardennes department in France.
Building of the Old Subprefecture was started in 1865 by the architect Auguste Reimbeau and completed in 1868 by the architect Jean-Baptiste Couty. It was built in a mix of architectural styles; Louis XIII, Renaissance and Louis XIV. It is a rectangular building within a walled garden, with an auxiliary building in its south west corner, bordering the river Meuse.
After its completion it housed the headquarters of the General Staff of the armed forces. It was also, briefly, the residence of Napoléon, the Prince Imperial. The Prince's father, Emperor Napoleon III, stayed here for 3 nights in 1870 during the Battle of Sedan, before he went to Bellevue Castle to surrender to the German Emperor, William I. Later it housed the local subprefects.
I could not find out when it was ruined.
At present the Old Subprefecture and its domain are not accessible and much overgrown. Although I have seen pictures on the internet of its interior, probably made by urban explorers who climbed over the garden walls. A wonderful gloomy ruin. The castles of Sedan, Bellevue and Villette are nearby.