The Pantheon

The Pantheon is a temple almost two thousand years old, and it still stands whole. Its concrete dome is the largest unreinforced dome in the world: forty-three metres across — exactly its height from floor to top.

2 excursions here

At the centre of the dome is a round hole, the oculus, nine metres wide. Nothing covers it: when it rains, water falls inside, and drains in the floor carry it away. Through the day the sunbeam from the oculus travels across the walls like the hand of a clock. Ask your child to follow where it gets to while you stand inside.