In 1851, physicist Léon Foucault demonstrated the rotation of the Earth with an experiment conducted in the Paris Panthéon. By constructing a fixed 67-meter swinging lead bob beneath the central dome, Foucault was able to prove that the earth was in fact in rotation at all times, as the plane of the pendulum never changed, yet it seemed to move with earth's rotation.
While the original pendulum is now housed at the Musée des Arts et Métiers, a working copy is displayed at the Panthéon and has been swinging there since 1995. Despite the history of the Panthéon, modern day achievements in the building are perhaps more fascinating.
In 2007, four members of the rogue art group Untergunther snuck into the Panthéon and restored the famous clock inside the building. Without being caught, the group decided to reveal itself and took credit for the work in front of the building administrator. Shortly after, the police were alerted, resulting in the arrest of the four members and a ridiculous trial in which the members of Untergunther were declared innocent.