The twin spires of Germany’s largest Gothic cathedral will soon be joined on the Cologne skyline by the minarets of the country’s biggest mosque. The $23 million Ehrenfeld Central Mosque, scheduled to be completed in about two years, will help bring Islam out of the back streets and reduce the influence of radicals, Mayor Fritz Schramma says. Others see the building as a symbol of Islamic extremism and further evidence that Cologne’s 120,000 Muslims, more than half of them Turkish immigrants, refuse to integrate. “I pray at the little chapel next to the Cologne Cathedral, and my prayer doesn’t become more valuable if I pray in the big cathedral,” said Laszlu Reischl, 56, a taxi driver. “I don’t understand why they insist on building a big mosque.” The controversy reflects Germany’s struggle over almost five decades to incorporate its largest ethnic minority. Tensions were revived in February when Turkish Prime Minister Recep Tayyip Erdogan told Turks at a Cologne rally that “assimilation is a crime against humanity.” Some lawmakers who oppose mostly Muslim Turkey’s bid to join the European Union accused him of preaching Turkish nationalism on German soil. Cologne has Germany’s highest concentration of Muslims, at 12 percent of the population. The new mosque will be built in the immigrant district of Ehrenfeld, about two miles from the 13th- century Cologne Cathedral. Seda Sezer reports.