Mont Saint-Michel Prison Interior, Normandy, France — After the French Revolution, the abbey was converted into a state prison holding political prisoners including priests who refused the Revolution's civic oath. Victor Hugo's vocal disgust at using a medieval masterpiece as a jail helped galvanize the preservation movement that converted it back to a historical monument in 1863.
© Kakha Kolkhi from Rouen, France, CC BY-SA 2.0, via Wikimedia Commons