The Sanctuary of Isis and Magna Mater in Roman Mogontiacum was built in the 1st century CE and remained in use until late antiquity. Archaeological remains came to light in 1999 during construction work in downtown Mainz for what is now the "Römerpassage", and were subsequently uncovered in a rescue excavation. Plans to demolish the ancient walls after the excavations were completed were abandoned following public protests; instead, a display room was set up at the site, where the most important architectural remains and selected artifacts are presented in a permanent exhibition. A comprehensive monograph detailing the results of the excavation has not yet been published.
Rediscovery, excavation and rescue In the late 1990s, the postwar buildings of the Lotharpassage in Mainz came into focus for urban redevelopment.Kullmann, Christof, "Die Lotharpassage," Deutsche Bauzeitung 130 (1996), 22; Dietz-Lenssen, Matthias, "Von Rosen und Schweinen. Kleine Geschichte der Lotharpassage," Mainz.Vierteljahresheft für Politik, Wirtschaft und Geschichte 22/2 (2002), 30–33; Heuser, Rita, Namen der Mainzer Straßen und Örtlichkeiten. Sammlung, Deutung, sprach- und motivgeschichtliche Auswertung (Stuttgart, 2008), 342. For the planned shopping arcade, then still known as "Lothar’s Passage," the existing buildings were demolished and a large excavation pit was opened. The project was accompanied by the Office of Historic Preservation of the State of Rhineland-Palatinate (Mainz Branch). Since the Roman road leading from the legionary fortress to the Rhine bridge passed through this area—sections of it were uncovered during the excavations—a typical provincial Roman row-house development in half-timbered construction with small workshops was to be expected.Witteyer, Göttlicher Baugrund, 4–5, idem, Sanctuary, 1.
However, in late 1999, two unexpected discoveries of considerable significance were made at a depth of about five meters: the remains of a Roman sanctuary, which could be attributed to Isis Panthea and Magna Mater based on inscribed blocks, and, beneath it, a burial site from the Hallstatt period that was about 700 years older. Over the following 17 months, the ancient building complex of the sanctuary and the Iron Age grave were carefully excavated and documented. For archaeobotanical and archaeozoological analyses, 15 tonnes of soil were removed; in addition, 49 m³ of recovered material was collected. The work was completed in early 2001.Witteyer, Sanctuary, 6–9. A monographic publication on the excavation results is still pending.In 2004, the publication of a scholarly edited volume with essays on various material and find groups from the excavation was planned, with publication envisaged by the publisher Philipp von Zabern. However, the volume was never published, so some find complexes remain unpublished to this day; Gorecki, Mos stipis, 209.
At first, it had been intended to remove the exposed remains after documentation and continue construction of the shopping mall as planned. A similar fate had already befallen a Mithraeum in Ballplatz square from the 1st or 2nd century in the 1970s: uncovered during construction work, it was only inadequately archaeologically recorded and was ultimately destroyed.Huld-Zetsche Ingeborg, Der Mithraskult in Mainz und das Mithräum am Ballplatz (Mainz, 2008). This time, however, protest emerged. In Mainz, a public debate flared up, and the newly founded initiative Römisches Mainz e. V.For more on the initiative, see in particular Krawietz, Peter, Das Heiligtum für Isis und Mater Magna in der Mainzer Römerpassage. Wie alles begann (Mainz, 2013). campaigned for the preservation of the sanctuary and collected around 20,000 signatures—an unmistakable vote against its destruction.Witteyer, Göttlicher Baugrund, 15. In addition, the initiative organized a demonstration led by university professor Helmut Mathy; see Dobras, Wolfgang, "Prof. Dr. Helmut Mathy (1934–2008). Ein Leben für die Mainzer Geschichte." Mainzer Zeitschrift. Mittelrheinisches Jahrbuch für Achäologie, Kunst und Geschichte 104 (2009), V–VII, here VII.
Public pressure was not without consequence. The ancient ruins of the sanctuary where permanently secured and integrated into the new mall. The public pressure did not go unnoticed. At the initiative's suggestion, the shopping arcade was named "Römerpassage"—a proposal that initially met with considerable resistance in the municipal committees but ultimately prevailed.Witteyer, Göttlicher Baugrund, 15; Heuser, Rita, Namen der Mainzer Straßen und Örtlichkeiten. Sammlung, Deutung, sprach- und motivgeschichtliche Auswertung (Stuttgart, 2008), 416. To proceed with the planned construction of the shopping mall façade, the remains had to be relocated: in a complex operation, part of the structural remnants was carefully dismantled and moved several metres, while the remainder was destroyed by the construction equipment. The preservation and relocation of the recovered remains cost approximately 3.5 million euros and were financed by the city of Mainz and the state of Rhineland-Palatinate.Witteyer, Sanctuary, 7; Funke, Bernd, Das Römische Mainz (Oppenheim, 2023), 128–129. Since its opening on 30 August 2003, when approximately 25,000 visitors streamed into the city centre, the sanctuary remains have been open to the public in a presentation room in the basement of the Römerpassage as the "Taberna archaeologica."For the opening ceremony, see Klose, Gerhild and Angermeyer, Katharina, "Isis hält Hof. Ein Römerfest zur Eröffnung der Kultstätte der Isis Panthea und Mater Magna in Mainz", Antike Welt 34/4 (2003), 521–524.
A glass walkway now runs around the exposed walls, while projections bring Isis and Magna Mater to life among the ancient foundations. Films, audio stations, and interactive elements complement the display cases containing the original finds. A staged ritual scene illustrates the daily practice of the cult; in an audio sequence, a fictional contemporary witness speaks about religious life in Roman Mainz in the 1st century CE. The space is kept deliberately dark to create a mystical atmosphere; small lamps set into the ceiling simulate the night sky of 21 December 69 CE. Information panels, along with a plan of the ancient city and of the sanctuary, complete the compact exhibition.Cf. Dolata, Jens and Witteyer, Marion: "Publikumsorientierte Geschichtsvermittlung – Die inszenierte Fundstelle des Heiligtums für Isis und Mater Magna in Mainz." Archäologie in Rheinland-Pfalz 2004 (2005), 40–43; Witteyer, Sanctuary; Brauch, André and Büllesbach, Rudolf, Römisches Mainz entdecken (Munich, 2020), 86. On the occasion of its 20th anniversary, the sanctuary was designated "Museum of the Month October 2023" by the Rhineland-Palatinate Ministry of Culture.Museumsblog Rheinland-Pfalz, Museum des Monats Oktober 2023: Heiligtum für Isis und Mater Magna (2023). Available at: museumsportal-rlp.de (Accessed: 27 March 2026).
Dating, dedication, and construction phases Although Tacitus casually reports toward the end of the 1st centuryTacitus, Germania 9.1. that among the Suebi the externally introduced Isis was venerated—while at the same time stating that he did not know the reason for this—this passage was long regarded as a misunderstanding, and the introduction of the Isis cult in Germania Superior was dated at the earliest to the mid-2nd century. Although plausible arguments for the historicity of Tacitus’ statement had already been made before the discovery of the Mainz double sanctuary,Haase, Mareile, "Signum in modum liburnae figuratum (Tacitus, Germania 9, 1). Überlegungen zum Beginn des Isis-Kults in Germanien," in Wolfgang Spickermann et al. (eds.), Religion in den germanischen Provinzen Roms (Tübingen 2001), 317–338. it was only the discovery of the sanctuary that provided conclusive evidence for the early arrival of the cult in Upper Germania.Nagel, Isis im Römischen Reich, 1191–1192.
A fragment of a building inscription with an engraved tabula ansata attests to the construction of the sanctuary by the treasury administrator Primigenius, who was subordinate to a procurator of emperor Vespasian (AD 69–79). The unexpectedly large number of roof tiles discovered in the sanctuary that bear military stamps may likewise indicate a state-organized construction project, although the evidence remains inconclusive. In the inscription, the divine addressee is named only as [Mater] deum, by which Cybele is probably meant. Two related tabulae ansatae with nearly identical inscriptions, dedicated by an imperial freedwoman and an imperial slave under the priest Claudius Atticus, mention instead the Magna Mater and Isis Panthea. The two inscriptions can be dated to the late 1st century and are dedicated to the welfare of the emperor, the Senate and the people of Rome, as well as the army. The inclusion of the army is unusual and is likely due to a local context. On the basis of the aforementioned inscriptions, a direct connection between the earliest construction phase of the sanctuary and the imperial household has occasionally been postulated; however, the arguments advanced in support of this are not compelling.
The establishment of a double sanctuary for the Magna Mater and Isis under Vespasian has parallels in Italy. The inscriptions indicate that both dedications were performed by the same priest, suggesting a personal union of the priesthood. Archaeologically, several building phases can be distinguished. In the initial phase, there were small rectangular cult buildings within an enclosing wall, as well as several half-timbered structures with hearths. The latter presumably served as kitchens and assembly rooms for ritual banquets. In these cult dining facilities, the services were likely provided that ensured the economic sustainability of the sanctuary. In the 2nd century, the small cult buildings were replaced by a large, multi-part structure with a stone base, a half-timbered superstructure, and its own well chamber. The interior spaces were only sparsely decorated. The cult activities continued at least until the end of the 3rd century; in Late antiquity, the structure was abandoned. Conclusions regarding the architectural development of the sanctuary can be drawn only to a limited extent, as the excavations did not expose the entire sacred precinct.Nagel, Isis im Römischen Reich, 1192–1193; Spickermann, Mysteriengemeinde und Öffentlichkeit, 139–141; Witteyer, Sanctuary, 26; idem, Gaben, Opfer, Deponierungen, 317–319; idem, Rogo te domina, 101–102 (with Fig. 1), 118; Gordon, Richard L., "Queering Their Pitch: The Curse-Tablets from Mainz, with Some Thoughts on Practising ‘Magic’." Journal of Roman Archaeology 27 (2014), 774–784.
Location and architecture The precise position of the sanctuary of Isis and the Magna Mater within the sacred topography of Mainz cannot be determined with certainty, owing to the lack of other clearly localizable sanctuaries within the urban area. Nevertheless, the location of the sanctuary itself allows for some conclusions regarding the considerations that likely influenced its establishment. The sacred precinct was situated along a heavily frequented main road leading from the legionary camp to the Rhine bridge. It thus occupied an important traffic axis and held a highly visible position within the public space. The sanctuary was located within the civilian settlement, which was enclosed by a defensive wall after the mid-3rd century.For the fortification of the civilian settlement in the 3rd century, cf. Heising, Alexander, Die römische Stadtmauer von Mogontiacum (Bonn, 2008), see in particular 157–179.