The most spectacular aspect is the size of the Pantheon. On the ground floor, in the form of a cross, it has a length of 110 m (352 ft) and a breadth of 85 m (272 ft.).

The dome with its height of 85m (272 ft) inspired the physicist Leon Foucault to carry out his first experiments with the pendulum in the middle of the 19th century. He wanted to demonstrated the rotation of the earth on its axis.