Pantheon

In 29–19 BC Marcus Vipsanius Agrippa built a temple on his own property in the Campus Martius, part of a complex that also included the Baths of Agrippa and the Basilica of Neptune. Pliny the Elder, who saw it, recorded that its capitals were of Syracusan bronze and its columns carved as caryatids by Diogenes of Athens, with statues on the roof; one half of a pearl belonging to Cleopatra was said to hang as an earring on a statue of Venus inside.

Fire destroyed Agrippa's building in AD 80; Domitian rebuilt it, and it burned again in 110. The present rotunda was finished under Hadrian and probably dedicated around 126, though the exact date is uncertain because Hadrian had the new building re-inscribed with Agrippa's own dedication rather than his own name – the facade still reads that Agrippa built it "when consul for the third time." Excavation later showed that almost nothing of Agrippa's temple survived beneath it except that facade. Writing about seventy-five years later, the senator Cassius Dio still attributed the domed building to Agrippa rather than Hadrian. In 202 Septimius Severus and Caracalla restored "the Pantheon ruined by age," as their own inscription on the architrave records.

In 609 the Byzantine emperor Phocas gave the building to Pope Boniface IV, who had the temple cleared of pagan use and consecrated it to St Mary and the Martyrs on 13 May 609; twenty-eight cartloads of relics were said to have been brought from the catacombs and placed beneath the high altar. Consecration as a church spared the building the abandonment and stripping that befell most of ancient Rome's monuments – though not its bronze: in July 663 the emperor Constans II, visiting Rome, stripped the roof of its bronze tiles and sent them to Constantinople, according to the chronicler Paul the Deacon. The roof stood bare for nearly a century until Pope Gregory III had it relined with lead in the 730s.

A belfry was added above the portico gable in 1270. Three of the eastern portico's granite columns were damaged or collapsed in the medieval period and were shored up with a brick and rubble wall, and by the 17th century the piazza outside had risen so high that visitors had to descend steps to reach the porch.

Since the Renaissance the building has held the tombs of the painters Raphael and Annibale Carracci, the composer Arcangelo Corelli and the architect Baldassare Peruzzi. In 1527 troops mutinying under Charles V, Holy Roman Emperor, sacked Rome and looted many of the building's relics; nine years later, after conquering Tunis, Charles visited it himself in a triumphal procession. According to legend, when the keeper's son guided him up to look down through the oculus, he felt a sudden urge to push the emperor through the opening in revenge for the sack; a different version of the story is told in Cervantes' Don Quixote.

Pope Urban VIII, who reigned 1623–1644, had the bronze roof trusses over the portico stripped and melted down, mostly to cast cannon for the fortification of Castel Sant'Angelo; a popular rumour that the metal went instead to Bernini's baldachin at St Peter's was later shown false from the papal accounts, but it produced the enduring jibe that "what the barbarians did not do, the Barberini did." Urban also replaced the medieval belfry with twin towers, designed by Maderno and his pupil Borromini and nicknamed "the ass's ears"; they stood until the late 19th century. Urban and, later, Pope Alexander VII between them cleared away the medieval wall that had propped up the damaged portico columns, replacing the missing shafts with granite columns salvaged from the nearby ruins of the Baths of Nero.

After Italian unification, two kings of the House of Savoy were buried in the Pantheon: Victor Emmanuel II, who died in 1878, and Umberto I, with Umberto's queen, Margherita. It had been intended as the resting place of the Savoy dynasty, but the monarchy was abolished in June 1946 and Italian authorities have since refused burial there to the former kings who died in exile, Victor Emmanuel III and Umberto II. The 17th-century twin towers were finally removed in 1883, and further restoration followed under the Fascist government from 1928, when the 18th-century plaster coating on the dome was stripped off and redone.

The Pantheon remains Italian state property and still functions as a working Catholic church: Mass is celebrated there on Sundays and holy days of obligation, and weddings are still held there.