The Panthéon is one of Paris's most imposing buildings — a neoclassical temple with a 83-metre dome that dominates the Left Bank skyline. Louis XV built it as a church in 1758; it was secularised during the Revolution and has served as France's secular mausoleum ever since, housing the remains of Voltaire, Rousseau, Victor Hugo, Émile Zola, Marie and Pierre Curie, and some eighty other figures of French intellectual life.
Foucault's pendulum hangs from the dome in a demonstration that became legendary when physicist Léon Foucault first suspended it here in 1851, proving the earth's rotation to a sceptical public. A reproduction swings permanently today.
The crypt is quietly moving — busts and inscriptions marking each sarcophagus, natural light filtering down from the rotunda above. Allow an hour. The surrounding Place du Panthéon has good cafes and bookshops catering to the nearby Sorbonne students.