The south terrace of this stadium is the most photographed stand in European football and, by one measure, the least profitable. Its 25,000 standing places sell for a fraction of a seat elsewhere in the ground.

Clubs in England and Spain, which removed standing areas decades ago, have begun to reintroduce them in limited form, citing atmosphere. Dortmund's executives are regularly asked how the numbers work.

The answer, they say, is that the terrace is not a revenue line but a marketing budget. The images it produces sell the club to broadcasters and sponsors in markets that have never seen a Bundesliga match in person.

“You could convert it to seats and make perhaps six million more a year,” said one executive, who asked not to be named because the club does not discuss pricing publicly. “And you would be a different club.”

Supporters' groups are less sentimental. They point out that the cheap terrace is also what keeps the stadium full when the team is losing, which is its own kind of insurance.