11 Monumental Facts About the Pantheon

The Pantheon, one of Rome’s most iconic structures, has stood tall over what is now known as the city's centro storico for nearly 2000 years. Below, a few things you might not know about the building, which draws tens of thousands of visitors each year.


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Marcus Vispanius Agrippa, a Roman statesman and architect, constructed the Pantheon starting around 27 BCE on his property in the Campus Martius. It was destroyed in a fire, however, around 80 CE, and a second temple built on the site was also ravaged by fire. 


Nearly 40 years after its initial destruction, the Emperor Hadrian had the structure rebuilt as (presumably) a temple dedicated to the gods. Agrippa’s mark remains, however: an abbreviated inscription on the front of the building reads Marcus Agrippa Lucii filius consul tertium fecit, which translates to “Marcus Agrippa, son of Lucius, Consul for the third time, built this.”


Along with other Roman structures that have withstood the onslaught of nature and time, the Pantheon has remained upright because of the use of a special kind of concrete. A combination of limestone and volcanic ash inside the concrete mix helped form crystals that prevented the spread of microscopic cracks.


The origins of the word Pantheon are Greek and refer to a temple dedicated to all the gods (Pan=all and Theon=gods). The ancient writer Cassius Dio references statues of various gods throughout the interior of the temple, but he himself was unconvinced about this etymology, preferring to think that it was because the vaulted roof “resembles the heavens.” Some modern scholars agree with Dio that the structure may not have been a religious building at all, citing its dissimilarities to other confirmed ancient temples. 


Measuring 142 feet in both height and diameter, the large interior dome is one of the highlights of the Pantheon. The thickness of the dome lessens as it climbs, going from 21 feet at the base to 4 feet at the top, thus lightening the stress of the weight of the roof. (In addition, different kinds of concrete were used, ranging from a density of 1600 kilograms per cubic meter to 1350 kilograms per cubic meter.) The dome was the largest constructed in the ancient world. 


Another remarkable feature of the Pantheon is the oculus, a 27-foot wide opening in the ceiling of the dome. The oculus, which is Latin for “eye,” is the only source of natural light in the interior of the Pantheon.



The exterior of the Pantheon includes a portico supported by Corinthian columns, a large pediment with the Marcus Agrippa inscription, and a second pediment attached to the rotunda. But the pediments don’t line up; the first, the Greek prosnaos, is about 13.5 feet shorter than the second, which is in line with the rotunda.

The mistake may be intentional, as the higher pediment lines up perfectly with the obelisk in front of the Pantheon, while the lower pediment matches the height of the obelisk at St. Peter’s Basilica. The most popular theory surrounding the height difference, however, is that the two pediments were going to be the same height until something happened to the planned columns, forcing the builders to compromise with the shorter columns that they had on hand.


While most scholars and historians have focused on the structural merits of the dome and oculus, Robert Hannah and Giulio Magli argue that the oculus may have been designed to represent a sundial. Visitors would be able to tell time by the passing of the sun overhead. What's more, the beams that shine through the opening also illuminate the doorway into the rotunda on the March and September equinoxes. 


In 609 CE, the emperor Phocas gifted the Pantheon to Pope Boniface IV, who then consecrated the building as the Church of Santa Maria ad Martyres. The continued use of the Pantheon is a major reason for its pristine condition 2000 years after it was constructed. To this day, the Catholic Church holds masses and weddings there. 


Starting during the Renaissance, the Pantheon was used as a tomb for artists like Raphael, Annibale Carracci, and composer Arcangelo Corelli. Italian kings Vittorio Emanuele II and Umberto I, along with Umberto’s wife Queen Margherita, are also entombed in the Pantheon.


The architectural majesty of the Pantheon has inspired numerous builders through the centuries. Filippo Brunelleschi modeled the dome of the Santa Maria del Fiore Church in Florence, Italy, after the Pantheon, and Louis XV commissioned Jacques-Germain Soufflot to build the Panthéon in Paris. Construction began in 1822 on the Rotunda on the grounds of the University of Virginia, which was designed by Thomas Jefferson and originally housed a library. It was still under construction upon Jefferson’s death in 1826. 

Penn Vet Working Dog Center
Stones, Bones, and Wrecks
New Program Trains Dogs to Sniff Out Art Smugglers
Penn Vet Working Dog Center
Penn Vet Working Dog Center

Soon, the dogs you see sniffing out contraband at airports may not be searching for drugs or smuggled Spanish ham. They might be looking for stolen treasures.

K-9 Artifact Finders, a new collaboration between New Hampshire-based cultural heritage law firm Red Arch and the University of Pennsylvania, is training dogs to root out stolen antiquities looted from archaeological sites and museums. The dogs would be stopping them at borders before the items can be sold elsewhere on the black market.

The illegal antiquities trade nets more than $3 billion per year around the world, and trafficking hits countries dealing with ongoing conflict, like Syria and Iraq today, particularly hard. By one estimate, around half a million artifacts were stolen from museums and archaeological sites throughout Iraq between 2003 and 2005 alone. (Famously, the craft-supply chain Hobby Lobby was fined $3 million in 2017 for buying thousands of ancient artifacts looted from Iraq.) In Syria, the Islamic State has been known to loot and sell ancient artifacts including statues, jewelry, and art to fund its operations.

But the problem spans across the world. Between 2007 and 2016, U.S. Customs and Border Control discovered more than 7800 cultural artifacts in the U.S. looted from 30 different countries.

A yellow Lab sniffs a metal cage designed to train dogs on scent detection.
Penn Vet Working Dog Center

K-9 Artifact Finders is the brainchild of Rick St. Hilaire, the executive director of Red Arch. His non-profit firm researches cultural heritage property law and preservation policy, including studying archaeological site looting and antiquities trafficking. Back in 2015, St. Hilaire was reading an article about a working dog trained to sniff out electronics that was able to find USB drives, SD cards, and other data storage devices. He wondered, if dogs could be trained to identify the scents of inorganic materials that make up electronics, could they be trained to sniff out ancient pottery?

To find out, St. Hilaire tells Mental Floss, he contacted the Penn Vet Working Dog Center, a research and training center for detection dogs. In December 2017, Red Arch, the Working Dog Center, and the Penn Museum (which is providing the artifacts to train the dogs) launched K-9 Artifact Finders, and in late January 2018, the five dogs selected for the project began their training, starting with learning the distinct smell of ancient pottery.

“Our theory is, it is a porous material that’s going to have a lot more odor than, say, a metal,” says Cindy Otto, the executive director of the Penn Vet Working Dog Center and the project’s principal investigator.

As you might imagine, museum curators may not be keen on exposing fragile ancient materials to four Labrador retrievers and a German shepherd, and the Working Dog Center didn’t want to take any risks with the Penn Museum’s priceless artifacts. So instead of letting the dogs have free rein to sniff the materials themselves, the project is using cotton balls. The researchers seal the artifacts (broken shards of Syrian pottery) in airtight bags with a cotton ball for 72 hours, then ask the dogs to find the cotton balls in the lab. They’re being trained to disregard the smell of the cotton ball itself, the smell of the bag it was stored in, and ideally, the smell of modern-day pottery, eventually being able to zero in on the smell that distinguishes ancient pottery specifically.

A dog looks out over the metal "pinhweel" training mechanism.
Penn Vet Working Dog Center

“The dogs are responding well,” Otto tells Mental Floss, explaining that the training program is at the stage of "exposing them to the odor and having them recognize it.”

The dogs involved in the project were chosen for their calm-but-curious demeanors and sensitive noses (one also works as a drug-detection dog when she’s not training on pottery). They had to be motivated enough to want to hunt down the cotton balls, but not aggressive or easily distracted.

Right now, the dogs train three days a week, and will continue to work on their pottery-detection skills for the first stage of the project, which the researchers expect will last for the next nine months. Depending on how the first phase of the training goes, the researchers hope to be able to then take the dogs out into the field to see if they can find the odor of ancient pottery in real-life situations, like in suitcases, rather than in a laboratory setting. Eventually, they also hope to train the dogs on other types of objects, and perhaps even pinpoint the chemical signatures that make artifacts smell distinct.

Pottery-sniffing dogs won’t be showing up at airport customs or on shipping docks soon, but one day, they could be as common as drug-sniffing canines. If dogs can detect low blood sugar or find a tiny USB drive hidden in a house, surely they can figure out if you’re smuggling a sculpture made thousands of years ago in your suitcase.

Big Questions
Why Don't Valentine Hearts Look Like Real Hearts?

Love is in the air this month, and images of two-lobed hearts are all over everything: candy, cards, decorations, you name it. That the heart is symbolic of love and passion isn't surprising—ancient Greek and Roman thinkers, including Aristotle, thought the organ was the center of all emotions. Why the heart symbol you see everywhere in February doesn't look anything like an actual human heart, though, is a little less clear.

The symbol goes at least as far back as the 1400s, when it appeared on European playing cards to mark one of the red suits, though it may even be older than that. The shape is pretty much a mystery, though. There are a few different hypotheses to explain it, but none of them have been confirmed.

One suggested origin for the symbol is that it comes from the ancient African city-state of Cyrene, whose merchants traded in the rare, and now extinct, plant silphium. The plant was used to season food, but doubled as a contraceptive. A silphium seedpod looks like a valentine's heart, so the shape became associated with sex, and then with love.

Another possibility is that the shape is a crude representation of a pubic mound, the vulva, a pair of breasts, buttocks, or a pair of testicles. It may even have come from a poor attempt at drawing an actual heart. A lousy artist, an inaccurate description of the subject, or a malformed model all could have led to that shape.

The Catholic church explains the symbol as coming from a vision that Saint Margaret Mary Alacoque had, where the "Sacred Heart of Jesus"—associated with love and devotion by Catholics—appeared in this shape surrounded by thorns. But Alacoque didn't have this vision until the late 1600s, well after the symbol was already documented. This makes it the unlikeliest of origin stories, but the church's frequent use of the shape was probably a driving factor in popularizing it as a symbol of love.

This story originally appeared in 2012.


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