The first building was put up in this location during the reign of Emperor Octavius Augustus. His friend and at the same time brother-in-law Marcus Agrippa, in the year 27 B.C., built a temple dedicated to all gods, although it is speculated that they were mainly those connected with the Julio-Claudian dynasty. According to the chronicler Cassius Dio, writing at the beginning of the III century A.D., it contained statues of Venus and Mars, meaning deities which in a particular way were connected with Julius Caesar and his foster son Octavius. The statue of Octavius, as well as one of Agrippa, was placed in the vestibule of this structure.

The building damaged during a great fire, which erupted at the Field of Mars in 80 A.D., was rebuilt by Domitian, however in the year 110 was once again damaged this time due to being struck by lightning. It was once again restored during the reign of Trajan and finished in the year 125 due to the endeavors of Emperor Hadrian. This time a truly solid construction was used, also taking into account the location of the Pantheon in a swampy region. The walls of the drum of the rotunda, which were 6 meters thick, were additionally strengthened at the base in order to place an imposing self-supported dome on it, with an oculus in the middle which had a diameter of nearly 9 meters and which was tasked with allowing light into the interior. Thanks to this very dome, created in the opus caementicium technique, using a material similar to concrete as the binder, this was a structure at that time changing all the known standards. It also became an inspiration of exceptional engineering thought for generations of architects. How were then, ancient architects able to construct a dome with a diameter of approximately 43 meters?

The thickness of the concrete layer was differentiated as the dome was being raised. The nearer we get to the oculus the thinner and at the same time lighter it is, thanks to combining the mortar with light, porous tuft. And that is why from the outside it looks slightly flattened, reminiscent of an upside down plate. In the bowl of the dome there are coffers, numbering 28, arranged in rows  which shrink and become more narrow as we approach the opening.

The walls and the floor of the rotunda which also has a diameter of 43.3 meters and just as much height are incrusted with multi-color marble tiles, travertine and granite. Seven exedras, among which there are aediculae with round or conic abutments, were designated for the exhibition of statues of deities. The purpose of the building at least since Hadrian’s time remains unclear. Some researchers claim that first of all it was a hall of meetings, today we would say a “conference center”, while only its secondary function was that of a temple, though one which did not have to serve any liturgical functions.

The tympanum of the vestibule is supported by sixteen columns from Egypt and Sardinia measuring 13.5 meters. It is decorated with an inscription reminding us of the initial founder: M[arcus] AGRIPPA L[uci] F[ilius] CO[n]S[ul] TERTIVM FECIT (Marcus Agrippa, the son of Lucius, erected this building when he became consul for the third time). And no word of Hadrian – the renovator of the building. The generosity of the emperor may be viewed as astounding, as in failing to mention his name, he reminded Romans of the initial founder. This is behavior which is truly rare under such circumstances. In such an approach historians see Hadrian’s foresight, since he was not very popular in Rome and very seldom stayed there, enthusiastically travelling throughout his empire, and had to be aware, how badly Romans reacted to Domitian’s decision to place his own name on the walls of the Pantheon when it was reconstructed for the first time. This gesture by Hadrian and this is something that the adopted emperor was conscious of, in a decisive way strengthened his position. He shows himself to be not as a person who had been „adopted” by his predecessor Trajan, when the previous emperor had been on his death bed, but as a continuator and protector of the tradition of the first emperors, in a way their equal.

Despite the fact that the building was closed during the times of Theodosius the Great (395) due to a struggle against pagan beliefs, it survived in an almost untouched condition for 214 years, which can be viewed as a real miracle. As one of the few buildings it was not taken apart in Christian times, when pagan temples generally fell into ruin and served as building material. This occurred due to the then ruler of Rome – the Eastern Roman Emperor Phocas, who desiring to protect this exceptional structure from destruction, presented it as a gift to Pope Boniface IV, who consecrated it and had bodies of Church martyrs from the nearby catacombs placed inside. Since that time, the Pantheon is a church dedicated to Our Lady and the Martyrs (Santa Maria ad Martyres).

In Hadrian’s time, the square upon which the Pantheon stands, was 1.5 to 2.5 meters lower than it is today. In time steps leading to the church disappeared in the ground which had raised through the centuries, while the church found itself in a sort of a depression. However, it is known that initially it was placed on a platfrom to which steps led and which towered over the travertine covered narthex (60 x 120 meters), surrounded from the north, east and west by a colonnade. Today this place is occupied by the Piazza della Rotonda, with a fountain which adorns it (Fontana della Rotonda). Looking at the Pantheon from the rear, we notice a rectangular structure added to its cylindrical form. These are the modest remains of a temple dedicated to the god Neptune – fragments of Corinthian columns as well as a frieze with dolphins.

The Pantheon was not again admired until the end of the XV century. It attracted the attention of Renaissance architects, who desired to imitate this masterpiece, especially its dome. It was recalled by Michelangelo in constructing his – over the Vatican Basilica (San Pietro in Vaticano). Reportedly the challenge put in front of him by his papal clients was clear. The dome of the greatest Christian church was to be in  a formerly pagan city the highest, but also the largest when it came to the diameter. And while the former part was completed in a masterful way, he was unable to succeed in the latter. The diameter of the dome of the Vatican Basilica is 1.4 meters smaller than the dome of the Pantheon. We do not experience this, since it does not have a drum, on which the dome of St. Peter’s Basilica rests. However the reason for our genuine admiration is not the fact that the Pantheon can successfully compete with the Vatican Basilica, but the elegance and dignity prevalent within, as well as the simplicity of the body. This is difficult to experience among the throngs of people who continually flow through this building. Only in the early morning, immediately after opening, in an empty interior we can experience its true, captivating beauty. And when the opportunity arises and raindrops begin falling inside, or the even more rare in Rome snowflakes, nobody will be surprised when we also begin to applaud this greatest work of human hands. However, there is no need for these meteorological phenomena to bring lumps to our throats, when we stand under the oculus and look upon the blue Roman sky. Or perhaps we will be lucky and the sun peeks inside, arranging a sort of a theatre of shadows, playing their game with the bright spots of the shining sun.