[de] Die evangelische Gemeindekirche St. Johannis im Zentrum von Mainz wird seit 2013 archäologisch erforscht. Sowohl Boden- als auch Bauforschung erbrachten Resultate, die es erlauben von St. Johannis als dem Alten Dom, der ersten Kathedrale von Mainz zu sprechen.Die Kirche St. Johannis steht auf profanen antiken Gebäuden, die zwischen dem 2. und 4. Jahrhundert errichtet wurden. Durch Umbau ging daraus im Lauf des 5./6. Jahrhunderts eine dreischiffige Architektur hervor, wahrscheinlich die erste Kathedrale von Mainz. Diese Kirche wich in der zweiten Hälfte des 10. oder im frühen 11. Jahrhundert einem Bau, welcher den Kern der heutigen Kirche bildet. Im Jahr 1036 erfolgte die Weihe des Neuen Doms, in St. Johannis gründete der damalige Erzbischof ein Männerstift. Die bipolare Kirche wurde im 18. Jahrhundert gewestet, 1793 profaniert und zum Militärdepot umfunktioniert, um schliesslich 1830 als evangelische Gemeindekirche geweiht zu werden.Die seit 2013 laufenden archäologischen Untersuchungen in der Mainzer Johanniskirche sind nicht die ersten. Anlässlich von zwei grossen Restaurierungskampagnen wurde Boden- und Bauforschung betrieben. 1905 leitete der Prähistoriker Ludwig Lindenschmit d.J. die Arbeiten, sekundiert vom Kunsthistoriker Rudolf Kautzsch. Die 1909 von letzterem publizierten Resultate lösten eine kontroverse Forschungsdiskussion um die Frage aus, ob St. Johannis vor 1036 die Kathedrale von Mainz war. Im Zuge des Wiederaufbaus nach dem zweiten Weltkrieg führten die beiden Kunsthistoriker Fritz Arens und Karl Heinz Esser (fig. 25-35) Ausgrabungen durch, welche auch von Bauanalysen begleitet wurden. Die Resultate blieben unpubliziert und die Fragen nach der Datierung und der Funktion der Kirche weiterhin offen. Erst die jüngsten Arbeiten, insbesondere die Entdeckung des Grabes von Erzbischof Erkanbald erbrachten diesbezüglich Klärung.

[en] St. John's (St. Johannis) Evangelical parish church in the center of Mainz has long kept the secrets of its architectural genesis and its early medieval status, despite numerous attempts to clarify this through sedimentary and building archaeology (Figs. 1-4). In recent years, an excavation has provided decisive evidence for identifying St. John's as the first and oldest cathedral in Mainz: St. Johannis is the "Alte Dom".The architectural beginnings of St. John's date back to antiquity, i.e. to secular buildings in the center of the Late Antique settlement, which can be dated between the 2nd and the 4th century (Figs. 1 and 5). During the 5th-6th centuries, part of the architecture was transformed into a three-aisled building divided by pillars, which was reworked several times. It was very likely the first cathedral in Mainz, where the first bishops are documented from the early Middle Ages. The building, dedicated to Saint Martin at the time, was replaced in the second half or the beginning of the 11th century by a three-aisled church with a kind of transept to the west and two choirs, the western one being built over a crypt (Fig. 8). This church lost its status as a cathedral in 1036 and became a collegiate church, dedicated to St John. A corridor, the so-called "Paradiesgang", linked it to the new cathedral built to the east (Figs. 1, 10, 11 and 12). After the reconstruction of the west choir at the end of the 14th century (Figs. 13 and 14), the orientation changed, apparently for town planning reasons: since the mid-18th century, the high altar was located in the west choir against its western wall (Fig. 15). In 1793, at the beginning of the French interlude in Mainz, St. John's church was desecrated and turned into a granary (Fig. 16), which it remained until 1830, the year of its re-consecration as an Evangelical Protestant church (Fig. 17). Two major restoration campaigns followed, from 1905 to 1907 (Fig. 18) and between 1949 and 1956, after World War II destructions (Fig. 19).The archaeological investigations in St. John's Evangelical Church in Mainz, which have been ongoing since 2013, are not the first. During the two major restoration and reconstruction campaigns, research was carried out on both the floor and the elevation (Fig. 20). In 1905 the investigations were led by the prehistorian Ludwig Lindenschmit the younger, with the expert and art historian Rudolf Kautzsch (Figs. 21-24). They carried out both ground and elevation surveys, which were documented by photographs and plans. It was finally the second, who was a professor at Darmstadt, who published the research. The main findings were that the present church dates back to the 10th century and is preserved under its very roof; it can also be identified as the first Mainz Cathedral. In its structure and method, Kautzsch's scientific essay is a jewel in the history of religious sites archaeology, although his much-discussed conclusions were rejected by the researchers at the time. The 1950-1951 research was initiated by art historian Fritz Arens, but was led by art historian and trained archaeologist Karl Heinz Esser (Figs. 25-35). Once again, the work concerned the underground and the masonries. The published summary dealt with all periods of the architectural genesis and did not contradict Kautzsch's opinion. But its publication in a local newspaper prevented its scientific reception. Scholars went on searching for answers to questions about the function and dating of St. John's.