It was explained to me that the hole in the pantheon is an optical illusion that is to say while standing inside it appears to be level parallel with the ground when it fact it is built at a steep angle thereby allowing light to come in normally but making it more difficult for rain to fall in.
Pantheon rome hole in roof rain.
The pantheon rome 8 31 smarthistory upon entry visitors are greeted by an enormous rounded room covered by the dome.
The hole in the top of the pantheon was to let in light and air.
The oculus at the top of the dome was never covered allowing rainfall through the ceiling and onto the floor.
Another beautiful effect takes place at pentecost when rose petals are sprinkled through the oculus after the annual mass.
Obviously being open to the elements means it also rains inside the pantheon but a gently sloping floor and 22 well hidden holes help the water to drain away.
Most believe however that the hole in its roof is a testament to rome s warm climate.
An architectural masterpiece no one quite knows how they rendered such a large dome from concrete.
Actually it s not covered because a roof could deteriorate the internal structure of the building.