This article accompanies the fable
This is said to be a photo of it but it is more likely a film reconstruction.
She was executed by firing squad on 15 October 1917 at the age of 41. The location as described by an eye witness was the "Caserne de Vincennes" (meaning, I assume, the military barracks known as Fort Neuf de Vincennes), which is shown below. I have no idea where the execution took place exactly but somewhere inside here. It is on the eastern side of the famous Château de Vincennes and its donjon (keep), which is shown at bottom.
Photos - above: Mike-tango; below: Selbymay