Greece & Rome · c. AD 330 · Ostia Antica, Lazio, Italy
Early Christian bishop's palace hall from Constantine's reign found at Ostia near Rome
Excavators found a marble-clad reception hall at least eight metres high beside a church built around AD 330, probably the seat of Ostia's bishops.
Official announcement
Ostia Antica, Italy Archaeologists working at Ostia Antica, the ancient harbour city of Rome, have excavated a large reception hall belonging to a bishop's palace beside a church built around AD 330, in the reign of Constantine the Great. The hall, found during the 2025 season, measured about 8 by 20 metres and is estimated to have stood at least eight metres high. Its walls were clad in marble and its floors laid with mosaic. The project's director, Sabine Feist of the University of Bonn, says nothing comparable is known from the period.
We have nothing comparable from the Constantinian period. Bishops were a newly rising elite in Late Antiquity, and they clearly adopted the architectural language of imperial and aristocratic power.
Sabine Feist, University of Bonn
The excavation is directed jointly by Feist, Michael Heinzelmann of the University of Cologne and Norbert Zimmermann of the German Archaeological Institute. Emanuela Borgia of La Sapienza University of Rome studies the pottery and small finds. The work is funded by the German Research Foundation (DFG).
From survey to excavation
The complex was first detected in 1996, when geophysical surveys by the German Archaeological Institute picked up a building of about 50 by 80 metres at the south-eastern edge of the ancient city. Full excavation began only in 2023. The campaigns of 2023 and 2024 exposed large parts of the church, which follows the standard basilica plan with aisles, an apse and a porticoed atrium in front of the entrance. It was built partly over an abandoned insula, a Roman apartment block of several storeys.
On the north side of the church the team found a baptistery with a circular font. The reception hall lay next to the apse end of the church. Besides fragments of coloured marble wall slabs and mosaic tesserae, the excavators found remains of a hypocaust, the Roman underfloor heating system, according to the Spanish science site La Brújula Verde.
The researchers identify the hall as part of the bishop's residence. Feist says there is no exact parallel anywhere in the Mediterranean for a hall of this kind attached to a bishop's church of the second quarter of the 4th century. Other buildings in Ostia have rich decoration, but the team says none matches this hall in size or luxury.
The contrast with the church itself is one of the puzzles the team now faces. The basilica, where the congregation met, is of fairly ordinary design. The hall where the bishop received visitors is far grander. La Brújula Verde's account reads this as two audiences being addressed: the local Christian community in the church, and civil and military officials in the hall, before whom the bishop presented himself with the same dignity as high imperial officials.
The find also settles a long-standing question about where Ostia's bishops had their seat. The Bishop of Ostia later became dean of the College of Cardinals, the cleric who convenes the conclave after a pope's death.
Saved by the plough
Ostia declined from the 3rd century as silt from the Tiber choked its harbour. The area around the bishop's church stayed inhabited into the early Middle Ages, longer than the rest of the city. Afterwards the land was farmed. Ploughing reached only a few centimetres into the soil and kept later builders away, so the complex escaped the medieval rebuilding that changed most large early churches.
This area was inhabited longer than any other part of Ostia. Here, we can study nearly 1,000 years of continuous settlement.
Sabine Feist, University of Bonn
Much of the complex is still buried. New funding has been approved for a further three-year project, and the team plans a six-week campaign in September and October 2026. It will investigate how the hall connects with the rest of the bishop's palace, which remains partly unexplored.
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