The Mithraeum at Ballplatz was a Roman sanctuary in the area of what is now the inner city of Mainz. It was located in the zone between Ballplatz square and Hintere Präsenzgasse, in the vicinity of today's Weißliliengasse. Its existence is attested by architectural remains, small finds, and several votive monuments, including a large marble altar with a complete dedication to Mithras. The complex was discovered in 1976 during construction work but was destroyed in the course of continued building activities, without any systematic excavation or documentation having taken place. In scholarship, an unusually early foundation of the temple, already at the beginning of the last third of the 1st century, has been repeatedly argued for. The sanctuary is considered an important piece of evidence for the presence of the cult of Mithras in Roman Mogontiacum.
Discovery and subsequent investigations Since the late 19th century, objects typical of a Mithras sanctuary have been unearthed in Mainz. However, these finds alone provided no clue as to the exact location of the associated temple.Hensen, Kult des Unbesiegten, 2023, p. 73, also p. 95, n. 2. In the summer of 1976, during the construction of a new office building for the Nordstern insurance company between Ballplatz square and Hintere Präsenzgasse, in the area of today's Weißliliengasse, extensive Roman building remains and artefacts were finally uncovered. In places, the mortared rubble masonry was preserved up to a height of roughly 90 cm; sections of the wall still showed traces of coloured plaster.
From the perspective of the Historic Preservation Office, neither archaeological supervision of the groundworks was planned nor was it possible to bring construction work to a halt. This was mainly due to the considerable shortage of staff at the authority, which, given the large number of simultaneous building projects in Mainz and Rhine Hesse, was unable to oversee all groundwork or to document and recover the findings through proper large-scale excavation. Compounding this was the fact that, in the absence of a legal framework, the authority had no effective legal means at its disposal, as the Rhineland-Palatinate Monument Protection Act had not yet come into force in 1976.Huld-Zetsche, Mithraskult in Mainz, 2008, p. 1; Hensen, Kult des Unbesiegten, 2023, pp. 73–74.
To make matters worse, numerous private individuals—so-called "history enthusiasts"—soon gathered at the construction site to search specifically for artifacts from the Roman era. Since the excavation work by the Cologne-based construction company was temporarily suspended, these unauthorized excavations were able to proceed largely undisturbed for several weeks, yielding a considerable wealth of finds. The activities of these individuals ranged from amateurish handling of the finds to outright criminal looting. Many of the finds recovered from the excavation pit were later resold, thereby permanently removing them from scientific research. In retrospect, the excavation must be regarded as a serious archaeological failure and a significant, irreversible loss from both a scientific and a heritage preservation perspective. The fact that the sanctuary did not, however, fall entirely into oblivion is due solely to a fortunate turn of events.Huld-Zetsche, Mithraskult in Mainz, 2008, p. 1; Hensen, Kult des Unbesiegten, 2023, p. 74.
Initially, the recovery of finds in the construction pit proceeded tacitly among those involved; however, a turning point came on 4 August 1976, when a large marble altar with a complete dedication to Mithras was uncovered.Ct. Huld-Zetsche, Mithraskult in Mainz, 2008, p. 82, cat. no. 565. After news of this extraordinary find became public, the authorities were notified; the altar, as well as other artifacts excavated by private individuals, attracted public attention for a time and were published in an initial report.Stümpel, Bernhard, "Bericht des Staatlichen Amts für Vor- und Frühgeschichte Mainz für die Zeit vom 1. Januar bis 31. Dezember 1976," Mainzer Zeitschrift 73–74 (1978/79), pp. 311−63, see p. 343; also pls. 58d–f. In addition, a significant find, a craterFirst published by Horn, Heinz Günter, "Das Mainzer Mithrasgefäß," Mainzer Archäologische Zeitschrift 1 (1994), pp. 21–66. Since then, a large number of additional studies on the crater have been published; see below. with figurative decoration and a painted inscription, was transferred to the collection of the Roman-Germanic Central Museum, where the cult vessel was restored in 1980/81.Huld-Zetsche, Ingeborg, "Der Mainzer Krater mit den Sieben Figuren," in Marleen Martens and Guy De Boe (eds.), Roman Mithraism. The Evidence of the Small Finds (Brussels, 2004), pp. 213–229, here p. 213. A considerable portion of the objects recovered at that time, however, was returned to the finders and can no longer be traced in its original form today.Huld-Zetsche, Mithraskult in Mainz, 2008, p. 1.
The official documentation carried out at that point was limited to a cursory survey of the wall remains and photographic recording of the still extant Roman masonry. A complete excavation did not take place, as significant parts of the context had already been destroyed. Accordingly, the interpretation of the complex as a Mithraeum was initially uncertain.Huld-Zetsche, Mithraskult in Mainz, 2008, p. 1; cf. also Hensen, Kult des Unbesiegten, 2023, pp. 77–78.
It was only the strong response that a renewed investigation of the "Mainz crater" by the archaeologist Ingeborg Huld-Zetsche received at an international conference in Belgium in November 2001,Huld-Zetsche, Ingeborg, "Der Mainzer Krater mit den Sieben Figuren," in Marleen Martens and Guy De Boe (eds.), Roman Mithraism. The Evidence of the Small Finds (Brussels, 2004), pp. 213–29. that led to the decision to undertake a comprehensive overall study of the temple context. For this project, Huld-Zetsche brought particular scholarly qualifications. As long-standing curator of the Roman department of the Archaeological Museum at Frankfurt, she had already dealt extensively with the material evidence of the Mithras cult, particularly in the course of evaluating the assemblages from the four Mithraea of Roman Nida in the present-day Frankfurt district of Heddernheim.Huld-Zetsche, Ingeborg, Mithras in Nida-Heddernheim (Frankfurt, 1986); also ibid., "Der Mithraskult im römischen Germanien," in Wolfgang Spickermann et al. (eds.), Religion in den germanischen Provinzen Roms (Tübingen, 2001), pp. 339–359. In addition, she specialised in Roman pottery. After retiring from active museum service, Huld-Zetsche, supported by the Mainz archaeologist Marion Witteyer, head of the branch Office of the Directorate of State Archaeology of the Department of Cultural Heritage (GDKE), Rhineland-Palatinate, began the scholarly examination and analysis of the surviving finds. In this process, material from a total of 13 private collections was systematically recorded and incorporated into the study.Huld-Zetsche, Mithraskult in Mainz, 2008, p. 1; ibid., "Ein Mithräum in Mainz," Archäologie in Rheinland-Pfalz 2002 (2003), pp. 75–78; Hensen, Kult des Unbesiegten, 2023, pp. 74–75. Huld-Zetsche's study has received widespread acclaim among scholars; for example, by Rainer Wiegels in Germania 87 (2009), pp. 641–644 and Richard L. Gordon in Klio 92/1 (2010), pp. 253–256.
Careful observation of the stratigraphic context by the private excavators yielded important insights into the temple's construction and phases of use. Taken together, these retrospective reconstructions provided, for the first time, a plausible picture of the temple's appearance and its immediate surroundings.Huld-Zetsche, Ingeborg, "Ein Mithräum in Mainz," Archäologie in Rheinland-Pfalz 2002 (2003), pp. 75–78; ibid., Huld-Zetsche, Mithraskult in Mainz, 2008, pp. 1–2. Alongside the Temple of Magna Mater and IsisFor more on this sanctuary, see Nagel, Svenja, Isis im Römischen Reich. Vol. 2: Adaption(en) des Kultes im Westen (Wiesbaden, 2019), pp. 1192–1197; Witteyer, Marion, "Rogo te domina. Bitten um göttlichen Beistand im Heiligtum für Isis und Mater Magna in Mainz," in Nina Gallion and Johannes Lipps (eds.), Beten in Mainz: Religion als Herausforderung in der Geschichte der Stadt (Oppenheim, 2023), pp. 101–23.—discovered in 1999, where the mistakes of 1976 were not repeatedWitteyer, Marion, Göttlicher Baugrund (Mainz 2003), p. 7.—the Mithras sanctuary is the only temple in Mainz whose location is known, although it must be assumed that the city had a significantly larger number of Roman religious buildings.Witteyer, Marion, “Rogo te domina. Bitten um göttlichen Beistand im Heiligtum für Isis und Mater Magna in Mainz,” in Nina Gallion and Johannes Lipps (eds.), Beten in Mainz: Religion als Herausforderung in der Geschichte der Stadt (Oppenheim, 2023), pp. 101–23, here p. 101.
Architectural reconstruction Ingeborg Huld-Zetsche bases her reconstruction of the sanctuary on the one hand on the official survey measurements of the Historic Preservation Office, and on the other on interviews with private excavators who had been present in the construction pit in 1976. Despite the fragmentary state of the documentation, three of the four characteristic features of a Mithraeum can be regarded as secure for the Mainz structure. First, the clear functional division of the complex into an approximately 22 m long and thus exceptionally large cult room (cella) and a possibly also subdivided antechamber is clearly attested. In addition, wall lines could be identified on both sides of the roughly 3 m wide axial corridor, interpreted as the inner boundaries of the benches. The rear wall of the cult room itself lay outside the excavated area and therefore cannot be examined more closely, so that no conclusions can be drawn regarding the specific form of the tauroctony setting; however, an altar base was found in close proximity to this area. Finally, a set of steps uncovered at the south-eastern end of the structure marks the architectural transition between antechamber and main cult room.
The remains of wall plaster are sparse, so that no reconstruction of wall or ceiling paintings is possible: stars on a blue background could not be identified; instead, the surviving fragments show patterns on a white background, as is also common in other Mithraea.
A northern entrance area is hypothesised, based on parallels from Martigny, where a cult shaft and coin finds mark the access point. In addition, an enclosure is assumed at a distance of about 6 m, as is typical for freestanding Mithraea, although there is no evidence for this in Mainz. This presumed enclosure is linked to the interpretation of pits containing Wetterau ware as ritual refuse pits; however, there is no direct evidence that these pits actually belonged to the sanctuary. For the surviving stone structure, Huld-Zetsche postulates an earlier wooden predecessor building.Huld-Zetsche, Mithraskult in Mainz, 2008, pp. 6–7; Hensen, Kult des Unbesiegten, 2023, pp. 78, 80, 91.