As part of an urbanistic research project to investigate the unexcavated areas of Ostia (1996-2002), geophysical prospections in the south-east of Regio V surprisingly revealed the remains of a large early Christian church complex, consisting of a three-nave basilica, a large atrium and baptistery, and an adjoining residential area. Subsequent stratigraphic soundings confirmed that we are dealing with the long-sought bishop's church of Ostia, which was jointly founded around 330 AD by Constantine the Great and Gallicanus, who was later canonised. At the same time, it became apparent that the basilica was built over an older insula of the Hadrianic period, the topped walls of which were deliberately used as foundations for the church complex. Remains of an early imperial building were found even lower down.

The Ostian church complex is of outstanding importance in several respects. From the perspective of church history, the basilica in Ostia is one of the earliest proper episcopal churches built outside Rome by Constantine, whose high ranking within the early church family is reflected, among other things, in the fact that the bishop of Ostia still holds the position of dean of the College of Cardinals today. From the point of view of architectural history, it is the earliest known standard basilica, i.e. a church that did not have to fulfil any special functions like Constantine's large church foundations in Rome or in the Holy Land, which means that it could have played a type-defining role in the later development of early Christian sacred architecture. Finally, the building complex in Ostia is the only Constantinian church foundation that has not been altered or destroyed by subsequent construction, which offers the unique possibility of an unrestricted archaeological investigation.

In a five-year project funded by the German Research Foundation and involving the German Archaeological Institute in Rome, the Universities of Bonn and Cologne, the Università 'La Sapienza' and the Parco Archeologico di Ostia Antica, a detailed investigation of the church complex is now to be carried out. The aim of these new investigations is to systematically excavate large parts of the basilica and its outbuildings in several sections. The focus will be on questions concerning the original design, furnishings and liturgical use of the Constantinian church building as well as subsequent adaptations and functional changes. In addition, the relationship of the church to the predecessor buildings below it should be better understood, thus providing new insights into the long-term urbanistic development of this area of the city.

Responsibles: Michael Heinzelmann, Sabine Feist, Norbert Zimmermann

Coordination: Hannah Boes, Arne Schröder

Cooperation: Deutsches Archäologisches Institut Rom, Abteilung Christliche Archäologie, Universität Bonn, Università ‚La Sapienza‘, Rom, Parco Archeologica di Ostia antica

Funding: Deutsche Forschungsgemeinschaft

Short information:

• Brief report on the excavation campaign 2023 in "Aktuelle Forschungen" (in German)
• Newspaper report at Vatican News (Excavation 2023, in Italian)
• Television report at RAI 3 (Excavation 2023, in Italian)