This is the Pantheon, a former church that now houses the tombs of many famous French people, thereby occupying roughly the same position in France that Westminster Abbey occupies in England. There are more than 70 people entombed here, including Marie Curie, Victor Hugo, Emile Zola, Jean Moulin, Voltaire, and many others.

The Pantheon was originally built as a church, on the orders of Louis XV, as a monument to Saint Genevieve. It wasn't completed until 1789, however-and that was just in time for the French Revolution, which promptly converted it to a necropolis for famous French people, rather than a church.

This building was also the structure in which Foucault conducted his famous experiment with a pendulum. A replica of his pendulum still swings slowly back and forth within the Pantheon. Most of the nave is walled off inside, so you can't actually get close to the pendulum unless you take the guided tour.

The dead people are in the very large crypt beneath the church. The crypt is nice in summer because it stays cool.