The Pantheon (UK: /ˈpænθiən/, US: /-ɒn/; Latin: Pantheum, from Greek Πάνθειον Pantheion, "[temple] of all the gods") is a former Roman temple, now a church, in Rome, Italy, on the site of an earlier temple commissioned by Marcus Agrippa during the reign of Augustus (27 BC – 14 AD). It was completed by the emperor Hadrian and probably dedicated about 126 AD. Its date of construction is uncertain, because Hadrian chose not to inscribe the new temple but rather to retain the inscription of Agrippa's older temple, which had burned down. The building is circular 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. Almost two thousand years after it was built, the Pantheon's dome is still the world's largest unreinforced concrete dome. The height to the oculus and the diameter of the interior circle are the same, 142 feet (43 m).It is one of the best-preserved of all Ancient Roman buildings, in large part because it has been in continuous use throughout its history, and since the 7th century, the Pantheon has been used as a church dedicated to "St. Mary and the Martyrs" (Latin: Sancta Maria ad Martyres) but informally known as "Santa Maria Rotonda". The square in front of the Pantheon is called Piazza della Rotonda. The Pantheon's large circular domed cella, with a conventional temple portico front, was unique in Roman architecture. Nevertheless, it became a standard exemplar when classical styles were revived, and has been copied many times by later architects.

In the center of the piazza is a fountain, the Fontana del Pantheon, surmounted by an Egyptian obelisk. The fountain was constructed by Giacomo Della Porta under Pope Gregory XIII in 1575, and the obelisk was added to it in 1711 under Pope Clement XI. The Aqua Virgo, one of the eleven aqueducts that supplied ancient Rome with drinking water, served the area of the Campus Martius, but had fallen into disrepair and disuse by the late Middle Ages. It was reconstructed under Pope Nicholas V and consecrated in 1453 as the Acqua Vergine. In 1570, Giacomo della Porta was commissioned under Pope Gregory XIII to oversee a major project to extend the distribution of water from the Vergine to eighteen new public fountains. Construction of the fountain in the Piazza della Rotonda was authorized on September 25, together with a fountain for Piazza Colonna, and two more for Piazza Navona; the fountain for the Rotonda, completed in 1575, was of a chalice-type design, around 3.5 to 4 meters in height, and fed with the Vergine water through a terracotta conduit. Della Porta designed the fountain, and Leonardo Sormani executed it. Due to the slope of the piazza, the fountain is approached by five steps on the south side, and only two on the north. Under the pontificate of Alexander VII Chigi, projects were set afoot to systematize the piazza and its setting, grading and enlarging it and widening the incident streets, in which Gian Lorenzo Bernini participated. An engraving by Giovanni Battista Falda records the work that had been completed at the time of Alexander's death in 1667. In 1711, the fountain was given its current appearance when Pope Clement XI had the Late Baroque sculptor Filippo Barigioni top it with a 20-foot red marble Egyptian obelisk. The obelisk, originally constructed by Pharaoh Ramses II for the Temple of Ra in Heliopolis, had been brought to Rome in ancient times where it was reused in the Iseum Campense, a shrine to the Egyptian god Isis that stood to the southeast of the Pantheon. It was rediscovered in 1374 underneath the apse of the nearby Basilica of Santa Maria sopra Minerva. In the mid-15th century, the obelisk had been erected in the small Piazza di San Macuto some 200 meters east of the Pantheon, where it remained until its 1711 move to the Piazza della Rotonda. It is still called the Obelisco Macutèo after its previous location.

Simone Pomardi (Monte Porzio Catone, 1757 - Rome, 1830) was a painter, draftsman and traveler. He was born in Monte Porzio by Giovanni Battista, notary and chancellor, and by Angiola Antonia Ilari, in 1783 he moved to Rome where he cohabited with some fellow artists, including Francesco Caucig and Giuseppe Bergler. It was noted, between the eighteenth and nineteenth centuries, for its large watercolors, almost always architectural subject, faithfully depicting Rome and its surroundings. He was the master of painting of Alessandro Castelli, his nephew from his mother. From his drawings the best calcographers of the time obtained etchings published in various books: Collection of ancient and modern views of the City of Rome and its surroundings engraved by various authors, 1816 (six drawings by Pomardi engraved by Antonio Testa and Pietro Parboni), Antiquities of Rome recently excavated up to the ancient floor designed by Simone Pomardi, 1817 (11 views of Rome and one of Tivoli), Antiquarian tour in the sorroundings of Rome by Antonio Nibby of 1819 (30 drawings by Pomardi engraved by Pietro Parboni), of XXXX Ancient and Modern Views of the City of Rome and its vicinity engraved by Morelli, Feoli, Ruga and other famous bullies (1821). He also collaborated on the illustrations of the Satyra V of Horace and Virgil's Aeneid published under the patronage of Elizabeth Duchess of Devonshire between 1816 and 1819. Between 1804 and 1806 Pomardi made a trip to Greece with Edward Dodwell, an Irish scholar. . The two performed many drawings and watercolors and about 800 of these works, preserved by Dodwell's heirs, remained unpublished until 2002 when they were purchased by David W. Packard, on behalf of the Packard Humanities Institute in Los Altos, California. A part of this extraordinary collection was exhibited for the first time at the British Museum and then in Rome in 2013 in the exhibition "The rediscovery of the ancient" set up in the Curia Julia of the Roman Forum. "The painted landscapes represent a rare testimony of the acropolis of Athens, the monuments of Mycenae, the port of Corfu and other archaeological sites as they appeared at the time of the Ottoman domination of Greece, seen through the eyes of the archaeologist and erudite Edward Dodwell, self-taught and talented watercolorist, and the Italian artist Simone Pomardi, already known for aquarelle paintings, rarely in tempera, in which he portrayed ancient Rome at the time of the French occupation. " A few years after his trip to Greece in 1819, Dodwell published A Classical and Topographical Tour through Greece during the years 1801, 1805, and 1806, with drawings by Simone Pomardi. In 1820 Pomardi published Journey in Greece made by Simone Pomardi, in the years 1804, 1805, and 1806, a detailed travel diary, covering not only the art and archeology but also the customs, customs and politics of the Greece of the time. "In this way Pomardi is the first Italian, if we exclude the inconclusive experience of Giovanni Battista Lusieri, to become the interpreter of the rediscovery of the historical and social world of Greece at the dawn of the nineteenth century following a line already opened by English and French "Finally, in 1821, Dodwell published Views in Greece from drawings by Edward Dodwell with some lithographs taken from Pomardi drawings. Serious health problems, which occurred around 1820, prevented Simone Pomardi from working. He died in Rome on 3rd November.