One of the most significant buildings of Roman architecture.
The original Pantheon was built under Agrippa in 27 - 25 BC as a temple. It was destroyed by fire in 80 AD and in 100 AD. The present building was built under Hadrian in c. 118 - 128 AD by an unknown architect and is among the greatest achievements of human architecture. Its exterior is rather unremarkable; all effort went into the splendid interior. The main building is of circular shape, covered by a hemispherical dome made of concrete; it is entered through a front porch with columns and a gabled roof. With a diameter of 43.3 m the dome was the largest of its kind for many centuries. The height of the building corresponds exactly to its diameter.
Light enters the building through a circular opening of 8.7 m diameter in the centre of the dome. Rectangular indentations in the dome serve to structure the interior and reduce the weight.
In 609 the Pantheon was dedicated to Christian service and became the church Santa Maria Rotunda, which it still is today.
Illustration: painting by Giovanni Paolo Panini, c. 1758; public domain (Wikipedia)