This plaque, bolted to the exterior wall of the mairie of the 3rd arrondissement, is all that's left of the building where Louis XVI and his family were held prisoner during the French Revolution. The prison was part of a larger fortress built by the Knights Templar in the Middle Ages. By the end of the 18th century, their power had long been broken and much of the old fortress destroyed. It was from here that the king was sent to the guilllotine in January 1793; Marie Antoinette was subsequently sent to the Conciergerie before she met the same fate. The prison was finally torn down for good in 1808 to prevent it from becoming a pilgrimage site for Royalists.
If you have a bit of imagination, go to the corner of rue Gabriel Vicaire and rue Dupetit-Thouars where this map will give you a sense of how the Temple's grounds relate to today's street map.
Special thanks to Jacques LeRoux who has taught me so much about Parisian history, art, architecture, and culture.