The present-day Pantheon is located on the site of an earlier structure of the same name, constructed around 25 B.C. by statesman Marcus Agrippa, son-in-law of the first Roman emperor, Augustus.

Traditionally thought to have been designed as a temple for Roman gods, the structure’s name is derived from the Greek words pan, meaning “all,” and theos, meaning “gods.”

The original Pantheon was destroyed in a fire around 80 A.D. It was rebuilt by Emperor Domitian, only to be burned down again in 110 A.D.

Hadrian became emperor in 117, a time when the Roman Empire included much of present-day Europe, as well as parts of the Middle East and northern Africa. Pᴀssionate about art and architecture, he embarked on a building campaign during his reign, which lasted until his death in 138.

Among these building projects was a defensive fortification, now referred to as Hadrian’s Wall, marking the northwest frontier of the Roman Empire. The wall measures 73 miles in length and stretches from coast to coast across modern-day northern England.

It’s unknown who the existing Pantheon’s architect was or exactly what role Hadrian played in the project. Evidence suggests the Pantheon was dedicated around 126-128 A.D., although construction might have started under Hadrian’s predecessor, Trajan, who served as emperor from 98 to 117.

It’s uncertain why, but Hadrian put Agrippa’s original inscription on the new Pantheon—“Marcus Agrippa the son of Lucius, three times consul, made this”—which led to centuries of years of confusion about its origins.

No one knows the original purpose of the present-day Pantheon, but Hadrian sometimes held court there.

In 330, the capital of the Roman Empire was transferred from Rome to Byzantium (modern-day Istanbul, Turkey) by Emperor Constantine.

Afterward, the Pantheon fell into a long period of disrepair. In 476, the German warrior Odoacer conquered the western half of the Roman Empire, where Rome was situated.

The Pantheon’s long decline continued. Then, in 609, Pope Boniface IV got permission from Byzantine emperor Phocas to convert the Pantheon into a Christian church, known as in Latin as Sancta Maria ad Martyres (St. Mary and the Martyrs).

It was the first Roman pagan temple to be consecrated as a Christian church. The conversion played a key role in the Pantheon’s survival, as the papacy had the resources to repair and maintain it.

Made primarily from bricks and concrete, the Pantheon consists of three sections: a portico with granite columns, a mᴀssive domed rotunda and a rectangular area connecting the other two sections.

Measuring 142 feet in diameter, the domed ceiling was the largest of its kind when it was built. At to the top of the dome sits an opening, or oculus, 27 feet in width. The oculus, which has no covering, lets light—as well as rain and other weather—into the Pantheon.

The walls and floor of the rotunda are decorated with marble and gilt and the domed ceiling contains five rings of 28 rectangular coffers.

When the artist Michelangelo saw the Pantheon, centuries after its construction, he reportedly said it was the design of angels, not of man. The Pantheon proved an important influence for the great Renaissance architect Andrea Palladio, as well as countless architects who followed, in Europe and beyond.

Thomas Jefferson modeled both Monticello—his home near Charlottesville, Virginia—as well as the Rotunda building at the University of Virginia, after the Pantheon. The U.S. Capitol rotunda was inspired by the Pantheon, as were various American state capitols.

Following the Pantheon’s conversion into a Christian church, it eventually became the burial place for Renaissance figures including painter Raphael, composer Arcangelo Corelli and architect Baldᴀssare Peruzzi.

Several monarchs are buried there too, including Vittorio Emanuele II, who died in 1878 and was the first king of Italy since the 6th century; his son, Umberto I, who was ᴀssᴀssinated in 1900, and Umberto’s wife, Queen Margherita, who pᴀssed away in 1926.

Today, the Pantheon is a major tourist destination for visitors from around the world, while continuing to function as a church. Catholic mᴀss is regularly held there.