Curious fact: Almost two thousand years after it was built, the Pantheon’s dome is still the world’s largest unreinforced concrete dome (sourcce: Wiki)
It is incredible the pictures you can take inside the building thanks to the circular opening in the middle of the ceiling…. Like this ones:
You can’t help but go there at different times of the day just to see how it looks like with the different angles of the sun beam. Should also be interesting when it is raining… I couldn’t see that, though… It was almost 40ºC in the week I was there…! But it is for sure interesting.