Constantinian Era Architecture at the Port of Rome
A few centimeters beneath the topsoil of a former agricultural field near Rome, excavations have uncovered the structural remains of a 4th-century episcopal complex. The site, located within the Ostia Antica Archaeological Park, contains a church and an adjoining palace dating to approximately 330 AD. Recent fieldwork in 2025 identified a formal reception hall, or aula, measuring 20 by 8 meters, characterized by marble cladding and mosaic floors.
Featured image: Aerial view: The two parallel stretches of wall in the foreground represent the double-shelled city wall, followed by the aula; in the center lies the baptistery with the circular baptismal font, and the atrium behind it. © Archiv Ostia-Projekt
The project is a collaborative effort led by Sabine Feist (University of Bonn), Michael Heinzelmann (University of Cologne), and Norbert Zimmermann (German Archaeological Institute). Heinzelmann has conducted research in Ostia for over two decades, while Feist specializes in Christian archaeology and architecture. The team also includes Emanuela Borgia from Sapienza University of Rome, who manages the ceramic finds.
The complex was first detected in 1996 through geophysical surveys conducted by the German Archaeological Institute. These surveys revealed a 50 by 80-meter perimeter at the southeastern edge of the city. Excavations funded by the German Research Foundation (DFG) followed in 2023 and 2024, revealing that the church was partially constructed over a repurposed insula, a Roman multi-story apartment block.
Ostia served as the primary port for Rome until the silting of the Tiber river led to its gradual contraction. While much of the city’s urban fabric shows terminal dates in the late Roman period, the episcopal site indicates continuous habitation into the early Middle Ages. The Bishop of Ostia held the historical office of Dean of the College of Cardinals, the figure responsible for consecrating the Pope and summoning the conclave.
The uncovered aula reached an estimated height of eight meters. Its scale and decorative programs—utilizing materials typically reserved for secular elite architecture—contrasts with the standard basilica form of the adjacent church. Findings include evidence of large-scale marble surfaces and floor mosaics that predate or exceed similar contemporary structures in the region.
Sabine Feist, who is also a member of the Bonn Center for Dependency & Slavery Studies, oversees the daily operations and coordination with Italian authorities. Documentation of the site involves drone photography, stratigraphic drawings, and digital mapping. The DFG has approved funding for a three-year extension of the project, with the next six-week excavation campaign scheduled for September and October 2026.
Source: uni-bonn.de
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