Dusted in marble, workmen scurry in the muted glow of stained glass. Some paint Koranic verses on the walls; others make last-minute alterations to golden-tipped minarets pricking a drizzly skyline. Anxious Berliners sometimes peek into the courtyard, where Ali Gulcek, a husky, nimble man, assures them his religion is not a threat.

"I need to enlighten the Germans so their prejudice of Islam will go away," said Gulcek, whose Islamic organization is building the mosque. "Our mosque will be completed in May. We've wanted a legitimate mosque for so long. For years, we've been meeting in backyards and basements. We don't want to hide anymore."

Gulcek's mosque is part of the surge in Islamic construction sweeping Germany. The number of traditional mosques with their distinctive minarets nearly doubled in Germany from 77 in 2002 to 141 in 2003, according to Islam Archive, a Muslim research group in the city of Soest. An additional 154 mosques and cultural centers are planned, many of them in the countryside, where vistas are dotted with symbols of crescent moons and crosses. 

Like the cultural battles over allowing Muslim women to wear headscarves in European schools, mosques are an indication that immigration is transforming social, religious and aesthetic landscapes. Staccato Turkish and throaty Arabic syllables whirl amid European vernaculars, and where once there was a German bakery there is now a Moroccan kebab stand. In some bookshops, the Koran is as prominent as the Bible, and Islamic worry beads sometimes rattle alongside rosaries.

Mosques are landmarks of faith. But in Europe they are also symbols of change that can instigate fear, especially as congregations at Christian churches steadily decline on a continent with the fastest-aging population in the world. A mosque often means a neighborhood is no longer what it was. Skin hues are darker, customs different, and society's failure at integration is laid bare.

For many Europeans since Sept. 11, mosques are perceived - unlike churches or synagogues - as caldrons of radicalism instead of places of worship. That sentiment is likely to endure if Islamic militants were involved last week's train bombings in Madrid that killed 201 people and wounded 1,500 others.

"Building a mosque won't create integration," said Werner Mueller, a pharmacist in a Berlin neighborhood where proposals for two mosques are encountering opposition from government agencies. "These new mosques will make Islam more visible, and jobless and angry Muslim men will go to them. They can become places infiltrated by political Islam."

Such sensitivity stems from the Al Quds mosque's link to Sept. 11: Mohamed Atta and other hijackers had regularly worshipped at the warren of rooms above a gym with smudged windows in Hamburg before they moved to the United States. Thousands of nondescript mosques, some tucked in alleys, others half-hidden in old factories, are scattered across Europe. There are nearly 2,400 in Germany alone, according to the Islam Archive.

The Berlin government is seeking more control over blueprints for larger mosques. The city's planning office wants veto power on all building projects that may impinge upon a borough's character. The veto proposal is expected to take effect this year and could complicate plans for four mosques in the city boroughs of Kreuzberg and Neukoelln. The government says it is not singling out mosques, but trying to bring uniformity to the skyline. 

"Berlin has a large Turkish population," said Petra Reetz, a spokeswoman for the planning office. "That always has to be a consideration. But we are still a Central European town and we'd like to keep the face of a Central European town, not a Turkish town." 

Such sentiments have made Mehmet Bayram a patient architect. The projects he treasures most, including mosques and Islamic cultural centers, are yet to be built, tangled in negotiations with government agencies. Bayram splices architecture, folding Islamic nuances into European designs to make Muslim edifices more palatable to the German eye. What could be considered minarets on the facade of one of his proposed cultural centers, for example, are instead spiraling stairwells.

Bayram described one project like this: "The main entrance gate has a European style, and on the third floor you will find Gothic arches. That is Christian architecture. The dome has a Turkish-Seldshuk form, and the little arches at the upper minarets are of Indian style... It is my intent that the building's street level invites visitors to overcome their fears" about Islam. 

"It's taken 13 years to build," said Gulcek, a smiling, yet exasperated, diplomat of sorts between cultures. "The biggest problem was raising money from Berlin Muslims. Then we found out our minarets were too high, and we had to raise more money for a $100,000 fine from the borough. Why? It came down to a misunderstanding. We didn't know about German law, and the borough didn't tell us.

"It was difficult to explain our idea of the mosque to the Germans. We should have explained it better," he said. "If you communicate, there are fewer problems, but there always seems to be a lace curtain between Germans and Muslims. Europeans have a prejudice and a fear of change."

Communication often seems impossible. Mosque proposals throughout the continent have met with opposition petition drives and street protests. Many mosques and their Islamic clergy exist in parallel, almost sequestered spheres from the larger European community. 

"The main problem with integrating mosques into German society is that many mullahs and imams are coming from Egypt, Saudi Arabia and other Islamic countries," said Lydia Nofal, manager of Inssan, a multicultural organization battling with government agencies to build a 65,000-square-foot mosque and community center in Berlin. "One of our main goals is to get Islamic leaders from Germany so they know the language and the culture." 

Navigating the sensitivities of race and religion can be difficult. On Sunday mornings, church bells peal throughout Europe's towns and cities. But in many mosques, the Muslim call to prayer, which in the Middle East crackles over loudspeakers atop minarets, is almost hushed. The devout check their watches for prayer times, and quietly kneel. 

The mosque building boom, mirroring the growth of an Islamic population in Europe that has doubled over the last decade to between 13 million and 15 million, may be most pronounced in Germany. But France, home to Europe's largest Islamic community, has 49 traditional mosques, including nine large ones in Paris. The estimated number of mosques in Britain - most of them converted buildings, apartments or prayer rooms with no minarets - has jumped from 613 in 1996 to about 1,000 today.

In Berlin's Kreuzberg borough, on a street scented with skewered lamb and spices and flecked with women wearing head scarves, Heidemarie Weigand and her husband, Hans-Juergen, were having a going-out-of-business sale at their toy train store. Heidemarie said her old customers had died or moved away and few newcomers were buying engines and cabooses these days.

"There's so many Turkish faces. There are hardly any Germans here, and the foreigners have no use for trains," said Heidemarie, her graying hair brushed back over a mauve sweater. "Many Germans aren't happy about the mosques. I don't think Turkey would like it if we went there and built a bunch of Christian churches."

A few doors down, Burhan Kesici, a soft-spoken man with a round face and a thin beard, sat in a green leather chair and spoke of the mosques his Islamic Federation in Berlin hoped to build. He believes in integration, he said, and even went against the wishes of his Turkish parents and wife by becoming a German citizen. Kesici understands the sensitivities that arise as Islamic culture deepens its imprint on Europe.

"There are a lot of new Islamic projects in the Kreuzberg-Neukoelln area," Kesici said. "The Germans may be saying, 'This is dangerous for us. There's too much of a concentration of religion in a small area.' But we Muslims have to be seen as normal. The mosques will allow us to show ourselves off better to society. We can help with the crime and social problems in these neighborhoods."

The Islamic Federation represents 26 Islamic organizations and 12 of Berlin's 75 mosques - only three of which have minarets. The federation, Kesici said, is in the midst of tedious negotiations with Kreuzberg borough on the design of a $4.9-million mosque and community center project. The government wants the federation to shrink the mosque by 40% so it will not overwhelm the neighborhood.

"The world is changing," said Kesici, who has a political science degree from the Free University of Berlin. "The European Union is expanding, and people are living with different cultures. I am a German and a Muslim. But the head scarf and mosque issues are showing us they don't want to accept our values. They're saying, 'You can be German, but a second-class German.' " 

Kesici's dream mosque, designed by architect Bayram, may remain a blueprint for several more years. Gulcek's mosque is stone and steel and colored-glass reality. It will open in two months. Christians and Jews and even secularists will be invited.