The Conciergerie

This is where the French Revolution ate its own. The Conciergerie served as the main prison during the Reign of Terror, and its most famous prisoner was Marie Antoinette, who spent her last 76 days here before being carted to the guillotine in October 1793. Her cell has been reconstructed and can be visited — a tiny room with a screen separating her from the guards who watched her around the clock.

Before it was a prison, the Conciergerie was a royal palace — the oldest surviving part of the medieval Capetian palace that once covered the entire Île de la Cité. The Salle des Gens d'Armes (Hall of the Men-at-Arms) on the ground floor, built in 1302, is the largest surviving medieval hall in Europe: a vast Gothic space with ribbed vaults supported by massive columns, where 2,000 palace staff once ate their meals.

During the Terror, roughly 2,780 prisoners were processed through the Conciergerie on their way to the guillotine. The wealthy could pay for private cells with beds and candles; the poor were crammed into straw-filled communal rooms called "pailleux." A list of those guillotined is displayed on the wall, and the names include not just aristocrats but also revolutionaries who fell out of favor — Danton, Desmoulins, and eventually Robespierre himself.

The building's four towers along the Seine are among the most recognizable features of the Paris skyline, especially the Tour de l'Horloge, which has held the city's first public clock since 1370. The clock still works, and it's been keeping time for over 650 years — through every revolution, war, and occupation the city has endured.