The Pantheon is a former Roman temple and since the year 609 CE a Catholic church (Basilica di Santa Maria ad Martyres or Basilica of St. Mary and the Martyrs), in Rome, Italy, on the site of an earlier temple commissioned by Marcus Agrippa during the reign of Augustus (27 BCE – 14 CE).
When it was initially built, the Pantheon was meant to serve as an assembly hall where the public could gather. Hadrian would have sat in a throne to oversee public gatherings. While meant to represent all gods as its name suggests, the Pantheon was not necessarily used as a temple because it lacked the rectangular shape of previous temples.
In part, the Pantheon was meant to appease the gods because the destruction of the previous buildings in its place was seen as a sign that the gods were unhappy. In the niches would have originally stood statues of various gods, and deified emperors. For example, a statue of Augustus was placed in one of the main recesses.
circa 120 CE
The building is cylindrical with a portico of large granite Corinthian columns (eight in the first rank and two groups of four behind) under a pediment. A rectangular vestibule links the porch to the rotunda, which is under a coffered concrete dome, with a central opening (oculus) to the sky. The Pantheon is one of the best-preserved of all Ancient Roman buildings, in large part because it has been in continuous use throughout its history.
circa 120 CE
Facade
Today the facade is fronted by eight monolithic columns topped by a frieze topped by a Greek-style pediment. The pediment was decorated with relief sculpture, probably of gilded bronze. The columns are made of red and gray granite and the shafts stand 40 Roman feet tall, carved in eastern Egypt. The building was originally approached by a flight of steps. Later construction raised the level of the ground leading to the portico, eliminating these steps.
circa 120 CE
Dome
The dome itself is created by overlapping barrel vaults over the third-story chambers. Almost two thousand years after it was built, the Pantheon's dome is still the world's largest unreinforced concrete dome. The dome spans 150 Roman feet; the oculus is 30 Roman feet in diameter; the doorway is 40 Roman feet high. The interior of the dome was possibly intended to symbolize the arched vault of the heavens. The dome features sunken panels (coffers), in five rings of 28. The oculus at the dome's apex and the entry door are the only natural sources of light in the interior.
circa 120 CE
Drum
The Pantheon’s drum, is a massive, cylindrical structure that forms the bulk of the monument. Though made of concrete, it is deceivingly light — the thicker sections of the wall accommodate empty, semicircular spaces. The drum’s solid appearance conceals its hollow interiors while maintaining its strength. The Romans invented and utilized a system of interlocking brick arches, vaults, and piers to enable the drum’s even weight distribution and support. From the outside, the monument seems dense but allows a hollow interior: this Roman technique can be seen in Trajan’s Column as well.
circa 120 CE
Rotunda
The height and diameter of the interior rotunda both measure 43.3 meters; the implication of this is that a perfect sphere with a same diameter would fit just perfectly inside the rotunda. The oculus, or opening at the top of the dome, measures 8.8 meters across and significantly lightens the load on the foundation of the structure. Serving as the major source of light in the Pantheon, the oculus also allows in rain and snow, setting a different atmosphere throughout the seasons. The floor is sloped towards drains that are present to collect rain. Blind windows line the rotunda, probably meant to let light into the extensive network of passageways that are used by maintenance crews. The marble work on the floor containing patterns of circles and squares is a 19th century accurate reproduction of the original floor.
circa 30 BCE
Basilica of Neptune
The Basilica dedicated to goddess Neptune (Basilica di Nettuno) was a basilica built in Rome by Marcus Vipsanius Agrippa in honour of Neptune and in celebration of his naval victories at Mylae, Naulochus and Actium. Near the site of the Pantheon, its remains were restored under Hadrian for an unknown use. It was part of building works on the Campus Martius between 33 and 25 BCE, possibly financed by the proceeds of Octavian's campaign in Illyria between 35 and 33 BCE. The project also included the Pantheon, the Saepta Iulia and the Baths of Agrippa.
circa 30 BCE
Portico of the Argonauts
The Porticus Argonautarum (Portico degli Argonauti) was an ancient structure in Rome. The building was located in the Saepta Julia, a large square in the Campus Martius used for public comitia (assemblies) and lined the western side of the Saepta Julia. The portico of the Argonauts was added in 25 BCE, to commemorate Agrippa's naval victories in 31 BCE: it took its name from its decorations, which depicted the mythological expedition of Jason.
circa 30 BCE
Macuteo Obelisk
This obelisk was originally erected by Rameses II as one of a pair at the Temple of Ra in Heliopolis, the other being the now much shorter Mattei Obelisk. The Macuteo Obelisk is 20.8 feet tall (47.6 feet with base), covered in hieroglyphics, and now stands in front of the Pantheon. The inscriptions contain phrases that indicate the kinship relation between the pharaoh and the Sun god ("Excellent son of the Sun god") and commemorate the works carried out in honor of the god. In 1711 it was erected in its present location on a pedestal decorated with a fountain with dolphins, adapting it to the 16th century fountain with masks by Giacomo della Porta.
