The most beautiful Roman vestige is without doubt the Pantheon. This temple has suffered so little, it seems like they had their time to see the Romans. I think this archway immense, hanging over his head for no apparent support, give the silly sense of fear; but soon calmed down and say: Is to please me who have taken the trouble to give me a feeling so strong! In the year 27 BC Agrippa, son-in-law and architect of Augustus, the Pantheon stands on the site where Romulus, according to legend, "ascended" to heaven during a ceremony. Is a common temple, rectangular, medium size, conceived as a place of worship for various divinity. Over the years, the temple suffered fires and other disasters, was restored several times until the emperor and architect Adriano rebuilt between 118 and 128 AD.

It is certainly of Adriano the pronaos with sixteen columns, the extesion of the “rotonda” and the dome – the broadest that ever was constructed in masonry – built with advanced techonoly. Adriano wants to remember the original architect, and restore the inscription on the pediment: "(Marco Agrippa, son of Lucio, Consul for the third time, built). In 608 Emperor Foca donated the temple to Pope Bonifacio IV who consecrated to Christian worship: Sancta Maria to Martyres, a masterpiece of Roman architecture and first example of transformation of a pagan temple into a Christian church. The temple stood on a staircase that starts from a lower level than the colonnaded square.

Originally the dome was covered externally with titles of gilt bronze scales, stolen in 663 by Emperor Costante II of the East and replaced by a covering of lead in 735. The same happened to the bronze covering of the porch, used to melt guns or granted by Urban VIII Bernini to make the canopy of San Peter. Few additions to the original architecture: the ornaments of the church, the tombs of great artists (Raffaello) and those of the King's of Italy. Always Bernini erected two ugly towers on either sides of the eardrum as “donkey ears", removed at the end of the nineteenth century. The Pantheon there are also busts fees that Pio VII had removed and transported to the Campidoglio, in the current Protomothèce (collection of busts of famous people).

Today the absence of the coating exposes the opus with brick arches which support the weight of the mole. The pronaos hides the view of the “rotonda” at the entrance to the space determined by a sphere inscribed in a cylinder, the finite and the infinite whole. The floor is covered with colored marbles and so did the walls supporting the dome terminates in a large circular aperture oculos 9 meters in diameter – that served to give light inside and as an outlet to the smoke of sacrificial fires. The axis of the building includes a small deviation in relation to North - South: each year, at 12, 21 June, summer solstice, the ray of sunshine through the eye involves the visitor entering from the main door.