Panthéon

The Panthéon was Louis XV's vow of thanks for surviving a serious illness in 1744 — a new church for Saint Genevieve, patron saint of Paris. Construction ran from 1758 to 1790, and the resulting neoclassical monument (with a dome inspired by St Peter's in Rome and St Paul's in London) was ready just as the Revolution decided France didn't need any new churches. It was reconsecrated as a mausoleum for the great men of the Republic in 1791.

The crypt is the reason to come. Voltaire (marble sarcophagus) and Rousseau (with a hand extending a torch) face each other across the entrance — deliberately, given their bitter 18th-century intellectual feud. Elsewhere: Marie Curie (the first woman interred here on her own merit, in 1995), Victor Hugo, Émile Zola, Jean Jaurès, Simone Veil, Josephine Baker (added 2021). Reading the plaques is a compressed history of what the French Republic has valued.

Upstairs, in the nave, hangs the reason many physicists come here: Foucault's original 1851 pendulum, a 67 m wire with a 28 kg brass bob, first used to demonstrate the rotation of the Earth (the plane of oscillation appears to rotate; in fact it's the floor beneath it turning). A replica has swung continuously since 1995.

The dome (€3.50 extra, 206 steps) opens April to October and gives a very different view of Paris from anything else on the tourist circuit — you're up on Montagne Sainte-Geneviève, looking out over the Latin Quarter with Notre-Dame close by. Combined ticket with the crypt is €13.