Raise your hand if you’ve walked through the center of Rome and cursed those bumpy cobblestones and thought why are they still used to this day in a modern city. Those small cubic stones—made from a volcanic rock called leucitite/leucititis —torture your ankles, trap your high heels, and turn every rolling suitcase into a noisy soundtrack all the way to your Roman accommodation. However, they tell a story that is as complex as it is fascinating… and just a few people truly know about it!

First of all, and contrary to what many people think, the sampietrini are not a leftover from ancient Rome—you know, the Rome of Julius Caesar and the Colosseum. Nope! Their story begins in the 1500s, when Pope Sixtus V (back then the head of the government in Rome) decided to revolutionize the streets of the Eternal City by paving the muddy alleys around the river Tiber. At the time, however, they were simply known as “serci” (the Roman word for “stones”). They changed their name only when they started being used on a large scale: “sampietrini” comes from St. Peter’s Square (“San Pietro” in Italian), where they were first laid around 1725, during the papacy of Pope Benedict XIII.

Sampietrini represented an extraordinary technical innovation compared to the river pebbles or the bricks that were used elsewhere: they were always the same size (about 4.7 x 4.7 x 7 inches), had a truncated pyramid shape that guaranteed stability, and were made from local material (they come from the Alban Hills area near Rome), i.e., they were cheap!

As mentioned, we’ve all cursed those cobblestones.

However, we have to admit they’re uncomfortable for exactly the same reasons they’re brilliant. Their surface is perfect for draining rainwater, which is essential in a city built on some pretty steep hills. It also helps when it (occasionally) freezes, making it harder to slip and fall (although you’ll definitely slip on wet rain… oops!).

The way they’re arranged in a “herringbone” or fan pattern distributes weight evenly, allowing the pavement to adapt to ground movements without cracking. And there’s the maintenance factor: a damaged sampietrino can be replaced individually, without having to redo entire sections of street. Sampietrini are an example of sustainability before the word was even invented! Finally, a problem particularly relevant in modern times in a city like Rome: a street paved with sampietrini can be dismantled more quickly in case of archaeological discoveries—which happens a lot!

Today Rome is divided. On one side are those who would like to put down smooth, accessible asphalt even in the historic center, and on the other are those who consider sampietrini part of the city’s identity and praise their maintenance advantages. What do you think?

Among the nearly 2 million sampietrini paving St. Peter’s Square, there’s one that has gained particular fame. It’s located in the southwest section of the Wind Rose—that’s the marble sundial that circles the central obelisk (the tall Egyptian monument in the middle of the square)—precisely where the Libeccio (a southwestern wind) is indicated, on the left side of the square as you face St. Peter’s Basilica. And it’s a heart. Or at least, it looks like one.

People call it “Er Core de Nerone” (“Nero’s heart” in Roman dialect). The reference is to the fact that the infamous emperor had his circus on this very square.

The most romantic version—and the one that circulates most among tour guides and couples looking for selfies—claims the heart was carved by Gian Lorenzo Bernini, the architect of the magnificent colonnade around the square. According to this story, he carved that symbol as testimony to never having found true love in his life. Another version of the legend attributes the work to Michelangelo, as a reminder of an unfortunate love. The problem is that Michelangelo died in 1564, more than a century before Bernini completed the square and certainly way before the “serci” were put in place. But you know, Roman legends never cared much about chronology.

The truth? Probably much more mundane. In 1817, an abbot and astronomer named Filippo Luigi Gigli transformed the Vatican obelisk into an enormous sundial, and some historians believe he was the one who inserted the decorative sampietrino into the Compass Rose pavement. Other experts claim it’s not even a heart, but a stylized ivy leaf on a fragment of recycled marble from Imperial Rome (a “spolium,” as reused materials are called).

What’s certain is that when the square’s pavement was massively redone in the 1930s, someone saved this little mystery. Today it’s a destination for romantic tourists, photographed from every possible angle. Who knows how many times we’ve stepped on it absentmindedly, not knowing that under our feet was a piece of Roman folklore still alive.

Every year some particularly creative tourist thinks that taking home a sampietrino “found on the street” is a harmless souvenir. Spoiler: it’s not. Sampietrini are a property of the city and removing them is a crime (and if you remove them from protected heritage areas, you risk to be jailed!).

Fines start at 500 Euros (about $550 US dollars) and increase depending on the damage caused. In 2019, two Dutch tourists were stopped with a backpack full of sampietrini: in addition to a hefty fine, they had to personally reposition the stolen blocks under the supervision of the municipal police!

If you’re really that in love with sampietrini, know that some clever entrepreneurs have turned them into a business. You can even eat them: for example, Pasticceria Fassi (Italy’s oldest gelato shop, active since 1880!) produces a single-serving frozen dessert called “sampietrino”—shaped like a little cube, with chocolate coating and your choice of flavors inside. And there are also “sampietrini” chocolate cube-shaped cookies from the Giuffrè pastry shop, which you can find in the Trastevere neighborhood!

If you’re fascinated by the idea of buying a sampietrino that lasts longer than a sweet treat, Rome’s artisan scene offers decidedly creative alternatives: