All Roads Lead to Rome

People stand on a bridge extending across the bottom of a giant well.
Students in the Sediments of Pediments Maymester 2023 course stand at the bottom of the 173-foot-deep Pozzo di San Patrizio in Orvieto, Italy.

What happens when an architectural historian and a geologist combine their expertise in the Eternal City?


Ask an architectural historian to name a fascinating place to study the ancient world, and Rome will be high on the list. Ask a geologist? Turns out Rome is equally fascinating — but for the opposite reason.

Through a geologic lens, Rome is a “very young” landscape, said Sara Gran Mitchell, associate professor of biology: “The city is built largely on rocks deposited by a huge volcanic eruption series that erupted within the last million years, which is not that distant. Geologically, those volcanoes are young and could erupt again. And the Tiber River is still actively modifying the area.”

“I love this description of Rome as a ‘young’ landscape because we never think of it this way,” said David Karmon, professor and chair of visual arts. “It contradicts the very idea of the Eternal City — but it’s completely true in the geological sense.”

While serving together on a committee several years ago, Karmon and Mitchell discovered their shared fascination with Rome and wondered: What if they teamed up and examined the region through each other’s lens?

Sediments to pediments

After a scouting trip, Karmon and Mitchell developed and co-taught a four-week Maymester interdisciplinary course in 2023, Sediments to Pediments: The Urban Geology of Rome, a course they offered again in 2024.

“While the two fields of geology and architecture actually have a lot in common, they aren’t usually in dialogue,” Karmon noted. “So it was amazing to see and understand this place in a totally different way. By studying the city through a geological lens, not just as an urban landscape, the disciplines of geology and architecture began to merge, even fuse together. Architectural history focuses on buildings from the ground up, but in this course the building became the last thing.”

“It's the crust on top,” Mitchell said.

People view an ancient Roman mosaic
Course members examine a moasic of Neptune, which lent its name of the Baths of Neptune in Ostia.

In Rome, students identified geologic materials used throughout the urban landscape — including limestone or travertine, tufa or volcanic stone, pozzolana or volcano sand (used in concrete), and alluvial clays (used to shape and fire terracotta and brick).

“One of the words that came up constantly was ‘palimpsest,’ which we used to connect the two fields,” Karmon said. The term refers to superimposed layers originating from different times, and it can be applied to architecture and geology.

“The students were open to wherever the course would take them,” he said. “They were so interested in pursuing these questions and finding connections between the fields.”

Monte Testaccio

For one of their site visits, Karmon and Mitchell took students to an unexpected spot in the city: Monte Testaccio. At first glance, the grassy hill appears to be a natural geologic feature of the landscape. But upon closer inspection, visitors discover otherwise.

“It is actually a refuse pile of broken ancient Roman pots,” Mitchell said. “Romans believed that if a pot was used to transport olive oil, you could only use it once. So they would break them and pile them up. Monte Testaccio is the size of a city block and 100 or more feet tall. Students were amazed that, even in a short period of time, a trash pile could make such a large geomorphic feature in the landscape.”

And the pot fragments, poking through the grass, tell their own story. The ceramic was made from rock or clay likely originating from North Africa, because at that point in time the Romans were importing their olive oil, Karmon and Mitchell explain.

People stand in a Roman aqueduct.
Course members stand in the Aqua Virgo, one of 11 aqueducts that supplied water to the city of Rome.

“Before working with David, I may have looked at a feature like Monte Testaccio just in terms of describing its physical aspects,” Mitchell said. “But then it became a story of how, as these empires grew, their ability to get rocks from different places also grew. It became tied into a richer story.”

“To see the complexity of the physical environment gives you an appreciation of the environments you inhabit and encounter every day,” Karmon said. “It’s all about the complex dynamics of how an environment is created. You bring that back with you. It shakes you up.”

“Every place has an ancient history,” Mitchell noted — and that includes Holy Cross.

“I begin my Introduction to Geology course by looking at buildings on campus and describing the rocks,” she said. “There are beautiful spiral ammonite fossils from 190 million years ago in the tiles on the floors of Smith Hall that you walk across every day; the headstones in the Jesuit cemetery are made of marble from Vermont; and the columns of both Dinand Library and St. Joseph Memorial Chapel are made of Salem Limestone — if you look closely, it is made of tiny bits of shells ground up 340 million years ago when the middle of the United States was a shallow ocean. It's mind-blowing.”

Merging the study of architecture and geology could also help us think more broadly about certain modern-day challenges, Karmon and Mitchell agree.

“In geomorphology and soil science these days, there is concern about soil erosion and loss of agricultural soils,” Mitchell said. “Geologically and biologically, soil is this miracle substance that makes growing food possible, but it's so easy to ignore. And it is eroding off our agricultural lands at rates that it will not be replaced.”

Modern architects usually skip over soil altogether, other than thinking about how to stabilize it so they can build, Karmon said: “But if you look at 15th-century and 16th-century architectural discourse, design began with the soil.” He is now working on a book on the topic.

By studying the city through a geological lens, not just as an urban landscape, the disciplines of geology and architecture began to merge, even fuse together.

David Karmon, professor and chair of visual arts

The intersection of the two disciplines also sparked conversations about preservation.

“At the sites, I found myself thinking about how our perspective on preservation of landscapes and cities changes when we emphasize how these sites are always evolving,” Karmon said.

“In geomorphology, there’s this idea that if there's been a change made to the landscape by people, we want to fix it,” Mitchell noted. “But what do you fix it to? Who are we fixing it for?”

The same questions can be posed about preserving a building.

“It’s a really interesting way to think critically about preservation,” Karmon said. “It's something every generation has to make its mind up about.”