In 27 b.C., Agrippa, son-in-law and architect of Augustus, erected the Pantheon on the site where Romolus according to the legend ascended to Heaven during a ceremony. It was a common temple rectangular in shape, medium size, conceived as a place of worship for various divinities. Through the years the temple suffered fires and other disasters, it was restored several times till the final reconstruction by the emperor-architect Hadrian between 118 and 128 A.D..
The pronaos with its sixteen columns, the enlargement of the rotunda and the dome, the largest existing one built in brickwork up to our time, are for sure by Hadrian. Hadrian himself wishing to commemorate Agrippa replaced word for word on the temple’s façade Agrippa’s original inscription: “Marcus Agrippa, son of Lucius, Consul for the third time, built”.
In 608 the emperor Foca handed it over to Pope Boniface IV who consecrated it as catholic church: Sancta Maria ad Martyres, masterpiece of the Roman architecture and first example of pagan temple transformed into catholic church. The temple stood originally on a base having a high staircase surrounded by a colonnaded portico on a lower level than the modern one. Originally the dome was externally covered by gilt bronze tiles stolen in 663 by the Emperor of East Constant II and later substituted by a lead covering in 735. The same happened to the bronze covering of the porticoes which was removed by the pope Urban VII and used for the casting of cannons and for the baldachin of St.Peter. Not many things were added to the original architecture: the church decorations, the tombs of great artists (Raphael) and those of the Kings of Italy.
Bernini added two ugly bell towers called “asses’ears” demolished at the end of the 1800’s. Inside the Pantheon there are also honorary busts which Pius VII had removed and transported to the Capitole, inside the Gallery (collection of busts of illustrious men) Nowadays the lack of coverings reveals the original brickwork structure with weight and thrust which support the ring. The pronaos hides the cupola from sights till the entrance in the space determined by a sphere which can be inscribed in a cylinder, finished and unfinished together.
The floor is covered with polychromatic marbles so as the walls which support the huge cupola culminating in the great eye at the summit, 9mt wide, which illuminated the whole interior and served for the smoke of the sacrifices.The axes of the building contemplates a small divertion from the traditional north-south direction: every year on the 21st June at 12,00am, summer equinoce, the sun through the eye invests the visitors entering from the main door.