Looking at the Pantheon from the front, we see 16 gray columns. Each column is 39 feet (12 meters) high and made of gray stone (granite) which came from
The main part of the Pantheon is one big round room. It is 142 feet (43 meters) wide. It is covered by a dome. The center of this dome is 142 feet (43 meters) above the floor.
The dome is made of concrete: a mixture of rock, sand, cement, and water. The Pantheon’s dome is still the world's biggest concrete dome built without metal to make it stronger.
Sunlight comes into the Pantheon only through an opening at the very center of the dome. Rain sometimes comes into it the same way. This opening is 30 feet (9 meters) in diameter.