Louis XV built the Pantheon after vowing to construct a church on the site of the ruined church of St. Genevieve if he recovered from an illness. The foundations were laid in 1758, but was not finished until the eve of the Revolution in 1789.
Revolutionaries, being a largely atheistic group (which I would think you would have to be to roll as many heads as they did and not think that it would ultimately come back to haunt you), converted the building from a church to a mausoleum.
In 1851, physicist Léon Foucault proved what everyone had long since known when he put up a large pendulum up to demonstrate the rotation of the earth.
Proving that not all surreptitious activities must be nefarious, Untergunther (a “cultural guerilla movement”) spent a year covertly repairing the Panthéon’s antique clockworks.
Architectural Style: Neoclassicism
Architect: Jacques-Germain Soufflot
Address: Place du Panthéon, 5e, Paris, France
Hours: Daily 10am-6pm (last entrance 45 min. before closing)
Cost: 7€ adults, 4.50€ ages 18-25, free for children 17 and under
(More Reformed Francophobe reading on the Pantheon can be found here.)