The Montagne Ste-Geneviève is topped by the grandly domed and porticoed Panthéon, Louis XV’s grateful response to Ste-Geneviève, patron saint of Paris, for curing him of illness. The Revolution transformed it into a mausoleum, and the remains of giants of French culture such as Voltaire, Rousseau, Hugo and Zola are entombed in the vast, barrel-vaulted crypt below, along with Marie Curie (the only woman), and Alexandre Dumas, of musketeers fame, who was only “panthéonized” in 2002. The interior is overwhelmingly monumental, bombastically Classical in design – and has a working model of Foucault’s Pendulum swinging from the dome. The French physicist Léon Foucault devised the experiment to demonstrate vividly the rotation of the earth: while the pendulum appeared to rotate over a 24-hour period, it was in fact the earth beneath it turning. Huge crowds turned up here in 1851 to watch the ground move beneath their feet, and you can do the same today. In summer, regular guided tours take groups up into the vertiginous cupola and out onto the high balcony running round the outside of the dome.