High atop the “montagne” (actually a medium-size hill) of St-Geneviève, the dome of the Panthéon is one of the city’s most visible landmarks. This erstwhile royal church has been transformed into a national mausoleum—the final resting place of luminaries such as Voltaire, Rousseau, Hugo, and Zola, as well as Marie and Pierre Curie, and—since 2015—four World War II heroes of the Résistance. Initially dedicated to St-Geneviève, the church was commissioned by a grateful Louis XV, who attributed his recovery from a serious illness to the saint. The work of architect Jacques-Germain Soufflot, who took his inspiration from the Pantheon in Rome, it must have been magnificent—the vast interior was clearly created with a higher power in mind. However, during the Revolution its sacred mission was diverted toward a new god—the Nation—and it was converted into a memorial and burial ground for Great Men of the Republic. This meant taking down the bells, walling up most of the windows, doing away with religious statuary and replacing it with works promoting patriotic virtues. The desired effect was achieved—the enormous empty space, lined with huge paintings of great moments in French history, resembles a cavernous tomb. The star attraction in the nave is Foucault’s Pendulum (named after the French physicist Léon Foucault, who invented it in 1851), a simple device—a heavy ball suspended on a long wire above markers—that proves the rotation of the Earth. After major restoration work on the dome, visitors can once again climb the Panthéon’s lofty dome between April and October (the highest spot in Paris until the Eiffel Tower was erected in 1889) to see the city unfurl in a higgledy-piggledy sprawl of gray rooftops. It’s a breathtaking sight, spreading all the way out past the Eiffel Tower to the high-rises of Paris’s out-of-town business district, La Defense.