This archaeological surprise lay only an inch or so beneath the topsoil. For centuries, plows had scraped to and fro above these early traces of Christianity, rolling many a stone aside—but without causing any major damage. Ultimately, it was even a stroke of luck that farmers kept on using the site up until the opening of the archaeological park of Ostia Antica not far from Rome.
"There are no buildings here to get in the way of our digging and hardly any graves or similar for us to have to be careful of,
says Professor Sabine Feist from the Department of Christian Archaeology at the University of Bonn, who is also a member of its Present Pasts Transdiscipinary Research Area and Bonn Center for Dependency & Slavery Studies Cluster of Excellence.
This is thus fertile ground for researchers—as it is for other reasons too: “Although we know of other churches from this early period, they were completely transformed during the Middle Ages,” something that did not happen here either.
However, it has been a hive of activity ever since the 2nd century CE, when the town—these days a suburb of Rome—grew thanks to its importance for trade and its port. Later, it began to decline when the river and the harbor basin silted up, hindering shipping.
For Christianity, however, this was the dawn of a new era: Having initially been the target of persecution, the faith was made the state religion of the Roman Empire in 380 CE, a shift that is also reflected in numerous buildings.
Archetype and model for later monumental buildings
Up until recently, there were not believed to be many of these left. On the surface, there was not much to suggest that one of the earliest churches was built here in the archaeological park some 1,700 years ago.
It served more or less as the archetype and blueprint for later monumental buildings such as Cologne Cathedral or Ulm Minster.
Emperor Constantine the Great favored Christianity and supported the building of churches, including that in Ostia—one of the earliest, largest and most sumptuous examples.
The Bishop of Ostia also came to be accorded the important role of Dean of the College of Cardinals, who is responsible for summoning the conclave after the death of a pope.
For a long time, nobody knew where exactly his seat had been located.
In 1996, geophysical investigations by the German Archaeological Institute unearthed a church complex on Ostia’s southeastern edge that was roughly 50 by 80 meters in size and that was subsequently dated to around 330 CE.
However, it was not until 2023 and 2024 that the first excavations took place, helped by funding from the German Research Foundation. These uncovered large parts of the church, some of which had been built atop the remains of a Roman insula—a multistory block of rented houses. Feist has been leading the project since 2022 alongside Professor Michael Heinzelmann from the University of Cologne and Professor Norbert Zimmermann from the German Archaeological Institute. When she took up her appointment at the University of Bonn in 2020, Feist got in touch with Heinzelmann, who by this point had already been conducting research in Ostia for over 20 years.
The three members of the team each brought a different discipline to the table: Heinzelmann was a classical archaeologist, while Zimmermann specialized in painting and Feist in architecture. Emanuela Borgia from Sapienza University of Rome and her team are responsible for small finds, particularly ceramics.
Aside from the huge church with its bishop’s residence next door, the researchers also stumbled upon another large annex during their excavation work. The latest investigations, conducted in 2025, revealed this to have been a grand hall, or aula, from the bishop’s palace. Measuring some 8 by 20 meters, this would have been unusually large. It was certainly the real surprise of the dig: A room at least 8 meters high and lavish furnishings suggested a degree of splendor that the researchers had not been expecting.
“There’s nothing else from the Constantinian period to compare to this,” Feist says. “The bishops constituted a new class in late antiquity, one that first had to get themselves established.” To secure prestige, they clearly drew on what people in the secular world also used to make a splash: vast halls, marble slabs and mosaic floors. “But the hall next to the basilica surpasses all other contemporary examples in Ostia that we know about,” the archaeologist points out. “Ostia is a wholly unique example.”
Weniger singulär, sondern eher Routine sind die Grabungsarbeiten. Die Wissenschaftlerin trägt Sicherheitsschuhe, lange Hosen und Kappe – letztere wegen der unbarmherzigen Sonne. Mehrmals war Sabine Feist zusammen mit Promovierenden und Studierenden von der Universität Bonn für die mehrwöchigen Grabungen vor Ort. „Es ist heiß und die körperliche Arbeit anstrengend“, schildert sie. „Aber ich freue mich auf jeden neuen Tag, weil immer Neues dabei herauskommt.“ Eine Kelle hat sie immer griffbereit – um direkt selbst mit anpacken zu können. Ihre Hauptaufgabe ist es, alles im Blick zu behalten und zu entscheiden, wo und wie weitergegraben wird. „Wir sind als Leitung außerdem für die Kommunikation mit dem italienischen Grabungsteam und dem Archäologischen Park verantwortlich“, berichtet die Wissenschaftlerin, die auch Mitglied im Transdisziplinären Forschungsbereich „Present Pasts“ und im Exzellenzcluster „Bonn Center for Dependency & Slavery Studies“ der Universität Bonn ist.
Working to a strict schedule
The dig team sleep in mobile homes on a campsite, and their days are action-packed: When the archaeological park opens at 7:30 in the morning, they are there waiting at the gate. After a walk round and a discussion of the day’s agenda, excavations begin in earnest just before 8 o’clock. They take a light snack at 9:30 and lunch around noon, after which most people retreat to a shady tree.
Although the actual digging stops at around 3 pm, it is now time to compile a record of the day’s work using drones, photos, drawings and descriptions. This analysis can last well into the night. Everyone comes together for dinner, though, which they eat at long tables set up between the mobile homes. “We’ll either cook, order pizza or go to one of the simple restaurants nearby.”
“A somewhat contradictory combination"
Casting her eye over the dig, Sabine Feist says: “The fact that the insula had a second life as the basilica meant that this site was inhabited for much longer than the rest of Ostia.”
Everywhere else, the traces of settlement end much earlier; only at the basilica are there finds dating into the early Middle Ages.
Here, we’re able to study the settlement site over a period of nearly 1,000 years without any gaps,” says the researcher enthusiastically.
What role did the church play in sustaining settlement for so long? Was the construction project well received in Ostia at the time? What is the situation with the main piece of the puzzle, the bishop’s aula? And how does the “run-of-the-mill” basilica fit with the unique nature of the bishop’s grand hall? For Feist, this is a “somewhat contradictory combination.”
There is still much to explore beneath the old topsoil at the archaeological park of Ostia Antica. The research team has already secured funding from the German Research Foundation for a three-year follow-up project, with the next six-week dig planned for September and October 2026. Sabine Feist is prepared: Her trowel, hat and safety shoes are all laid out and ready for some serious excavating.
Pop quiz
What was the biggest challenge during the dig? Keeping track of everything. What did you find yourself thinking about most often? My two daughters. What was your most personal discovery? How well all the students from Bonn and Cologne know the words to the Carnival songs. Who from around the time the church complex was founded would you like to have a conversation with? Gallicanuns. He is named as a founder alongside Constantine the Great but, unlike the emperor, he was actually in Ostia himself. I’d like to ask him whether he owned the insula where the church was built. Was anything agreed with the imperial dynasty about establishing the church, or did he have a free hand? What’s been your favorite find? The aula in the bishop’s palace. Uncovering something that nobody knew about before is bound to get any archaeologist excited. Bio After studying Christian archaeology, the history of Byzantine art, classical archaeology and ancient history in Freiburg, Athens, Basel and Göttingen, Sabine Feist went on to do her doctorate in Munich from 2012 to 2016. She worked as a research associate at Martin Luther University Halle-Wittenberg between 2015 and 2020 and covered the Chair of Late Antiquity and Byzantine Art History at Ludwig-Maximilians-Universität München[HE1] from 2019 to 2020. She has been Professor for Christian Archaeology at the University of Bonn since 2020. Her research focuses on depictions of holiness[HE2] , late antiquity and Byzantine sacred architecture as well as the history of Christian archaeology as an academic discipline.
Fotos: Archiv Ostia-Projekt
Foto Sabine Feist: Barbara Frommann / Uni Bonn
Danksagung:
Photos: Archiv Ostia-Projekt Photo Sabine Feist: Barbara Frommann / Uni Bonn