DORTMUND, Germany — The ramps and slopes of the skateboard hall are stacked with thousands of donated garments, all sorted into boxes by type and size. The bowling lanes are dormant. The concerts and dance classes are postponed. Nothing ordinary has been happening at the Dietrich Keuning Haus, a community center behind the main railway station, since Sept. 6.

For 11 frenzied days, the building’s main hall served instead as a makeshift processing center for 8,000 asylum seekers in dire need of food, clothes and refuge.

Even before Germany opened its borders to a new wave of migrants this month, Dortmund’s main processing facility was overwhelmed. Intended to accommodate up to 350 people staying a week or two, the facility was swamped with as many as 1,500 refugees a day, and repeatedly had to suspend the reception of new arrivals.