A Christian, a Jew and a Muslim walk into the same house of worship...

IT IS USUALLY bad news when multiple religions claim the same place of worship. It can lead to conflict, as illustrated by the recent violence at Jerusalem’s holiest site. Or it can be a sign that flocks are dwindling, forcing congregations to share space. But Berlin’s House of One intentionally puts a church, mosque and synagogue under a single roof.

The cornerstone of the €47m ($57m) place of worship was laid last week near Alexanderplatz. In four years’ time, it will be a structure housing three separate prayer rooms and a 46m-high domed hall for the faiths to mix. “We are building the House to make a statement,” says Rabbi Andreas Nachama, one of the project’s leaders.

The idea has been in the works for a decade, since local leaders from the three Abrahamic religions came together to think up a plan for a religiously significant spot: the former site of one of Berlin’s oldest churches.

An interfaith project made more sense than another church, says Father Gregor Hohberg, a Protestant pastor whose congregation once worshipped at the site. “In Berlin we have a lot of very wonderful churches,” he points out. “And all of these churches are not full of people on Sunday mornings.” Berlin, after all, is better known for sex clubs and party drugs than piety. Still, another 120 people have already joined Father...