The Conciergerie occupies the oldest surviving part of the medieval royal palace on the Île de la Cité, its riverfront towers a landmark on the Seine. After the kings moved out it became a courthouse and prison, and during the Revolution it was the grim antechamber to the guillotine: more than 2,700 people were held here before execution, Marie-Antoinette among them, and her cell is reconstructed inside.
Behind the stern façade is one of the finest secular Gothic interiors in Europe — the vast vaulted Salle des Gens d'Armes, built around 1300 for the royal household. A joint ticket with the neighbouring Sainte-Chapelle is the sensible way to see both.