From the outside, the Catholic church in Mannheim's Neuostheim district appears to be a typical 1950s church building: a relatively simple structure, nothing particularly remarkable about it. Yet St. Pius is truly unique. In this place of worship, Catholic and Protestant Christians celebrate services sharing the same space and taking turns in gathering around the same altar for Communion and the Eucharist.

"It actually began in the early 1970s," Annette Hübner, a Catholic parishioner, told DW. The 57-year-old has lived in the district with her family for more than half a century and is a member of the parish team. At the time, the parish priest of St. Pius was committed to fostering cooperation with the Protestant community and began holding ecumenical services in 1970. Then, at the end of 2009, the nearby Protestant St. Thomas Church sustained extensive water damage, and the building was found to be beyond repair.

What began as a temporary arrangement gradually evolved into a lasting solution. That lasting solution, in turn, grew into a genuine ecumenical friendship.

"It became increasingly clear that it made sense to continue working together," Hübner recalled. A banner on the facade of St. Pius proclaims: "One Lord, one faith, one baptism." What may sound like a theological phrase from a Sunday sermon is part of everyday life here, on weekdays as much as on Sundays.

Catholics and Protestants under one roof: Germany is home to 65 so-called Simultankirchen (shared churches). Their joint use was mandated by secular rulers soon after the Reformation and the resulting division of the Church. In some cases, detailed regulations even specified who was allowed to enter the church and at what times. The best-known examples are Altenberg Cathedral near Cologne and St. Peter's Protestant Cathedral in the eastern German city of Bautzen in Saxony.

In hospital and airport chapels, shared use by different Christian denominations is now almost taken for granted. A similar trend, however, is increasingly emerging in ordinary parish communities. Protestant and Catholic churches in Germany's most populous state of North Rhine-Westphalia had already begun addressing the issue in 2017, during the commemorations marking the 500th anniversary of Martin Luther's Reformation.

"What If We All Moved In Together?" is the title of the Practical Guide to the Ecumenical Use of Churches and Parish Halls. The publication presents examples from the dioceses of Cologne and Aachen, as well as Essen, Münster and Paderborn.

The guide repeatedly points to the "accelerating reduction in church buildings." According to official church statistics for 2025, Germany had 24,500 Catholic and 21,100 Protestant churches, ranging from small chapels to grand cathedrals. Each year, dozens of churches are decommissioned, demolished or repurposed.

Attending a Protestant church was once considered 'a sin'

Examples of new shared church spaces can be found in both western and eastern Germany. In Schildow, on the northern outskirts of Berlin, only one church is expected to remain in use in the future: the larger and more prominent Protestant church. The Archdiocese of Berlin's press office describes the initiative as "an ecumenical project with exemplary character." Its statement also hints at the significance of this development: "For all the ecumenical openness that is now taken for granted," the Catholic participants still remember "earlier times when even attending a Protestant church was considered a sin."

Small congregations in the East

Catholic bishops in eastern Germany are quite accustomed to celebrating Mass in Protestant churches. For major occasions such as confirmations or parish anniversaries, the generally smaller Catholic churches are often unable to accommodate everyone. In such cases, their Protestant counterparts are often happy to provide the necessary space.

The German Bishops' Conference is also currently addressing the issue and plans to publish a practical guide on the subject. Here, too, the focus is on declining membership, church buildings that are no longer needed, financial constraints, and the potential for shared use.

Two altars merged into one

But St. Pius in Mannheim is different. It is far more than a temporary arrangement born of necessity. Here, the two congregations have developed a deep and wide-ranging form of cooperation. Between 2020 and 2022, the church underwent extensive renovation and redesign. The place where the altar once stood is now occupied by the baptismal font, serving as a shared focal point for both churches. A new altar, crafted from red and grey stone, now stands in the nave.

"The red sandstone comes from the altar of the Protestant church, and the grey travertine from the altar of the Catholic church," Hübner explained. Both were crushed and cast together to form the new altar. Parts of its surface are completely smooth, while others remain rough, with visible grooves and fissures. "It was a beautiful symbol of the relationship between Protestants and Catholics. We want to come together. But there are still points of friction and unresolved questions."

Careful legal arrangements

St. Birgitta-Thomas Church in the northern German city of Kiel can likewise look back on decades of ecumenical cooperation. Since 1980, the Catholic parish of St. Birgitta and the Protestant Thomas congregation have shared both the church and the parish hall. Here, too, this "sharing" is governed by carefully defined legal arrangements.

Officially, the church belongs to the Catholic parish, while the parish hall belongs to the Protestant congregation. "But we use both parts of the complex jointly and on an equal footing," Pastor Rebekka Ulrich told DW. With a smile, she adds: "The Protestant side leased the printer, but the Catholic side uses it too."

The 36-year-old pastor sees "an incredible number of points of overlap." These include joint worship services, celebrations and ecumenical dialogue. Each year, the two denominations adopt a shared motto. A hymn of the month, selected alternately from the Protestant hymnal and the Catholic Gotteslob, is sung by the entire congregation during services.

A shortage of clergymen and organists

The close partnership extends even to church music: both congregations share the same organist. "On Sundays, he accompanies the Catholic Mass at 9:30 a.m. and then the Protestant service at 11:00 a.m." If only everything were that simple. As Ulrich explains, the steadily declining number of Catholic priests is creating growing challenges for the Catholic side.

In Mannheim, Annette Hübner described the process as a journey that was long but, in her view, well worth the effort. The number of clergy is declining in both the Catholic and Protestant churches. At the local level, services of the Word conducted without a priest or pastor are becoming increasingly common.

Even the Eastern Christian tradition has found a place here. Since 1971, Mannheim has been home to the "Eastern Church Center Cyril and Methodius," which has been based at St. Pius from the very beginning. Once a month, a Catholic liturgy is celebrated according to the Byzantine Rite. Since the renovation, the church entrance area has included a specially designed space with icons and a symbolic iconostasis. All of this exists under a single church roof.

This article was translated from German.