When you sit down and talk about issues in Germany....a fair number of these issue relate back to density of the particular German state you are talking about (one of the sixteen). Few people ever visualize Germany in terms of density.
The three 'kings' of density in Germany are Berlin, Hamburg, and Bremen. Oddly, Brandenburg and Mecklenburg are at the bottom in terms of density. If you add up the top three and compare against the bottom two....the bottom two are two-percent of the combined top three.
Each of the top three? If you bring up crime, integration issues, public frustration....it tends to gather more in highly urbanized areas of Germany.....not in the lesser urbanized areas.
Ethnic diversity in these highly urbanized states? This is another interesting topic.
If you go to North Rhine Westphalia.....there are ten significant communities often talked about. The Turks and Kurds always get talked about. The lesser groups? The Italians, the Dutch, the Poles, the French, the Arabs, the Iranians, the Indians, and strangely enough....the Japanese (a large community in Koln).
When you go to Berlin....there are a minimum of 20 different ethnic groups in the region: the Turks, the Kurds, the Vietnamese (left-overs from the DDR years), the Arab community, the Bosnians, the Poles, the Russians, the Albanians, the Serbs, the Israelis, the Chinese, the Africans (multiple countries), the Chileans, the Brazilians, and the Americans. Americans are thought to now number in the 20,000 range. Some are part of the new IT sector that is growing, and others are simply part of the Berlin-cultural crowd (art, literature, cinema, etc).
When you go to Hamburg....there are probably a dozen significant ethnic groups in the city-state:
the Turks, the Kurds, the Russians, the Africans (various nationalities), the Poles, the Albanians, the Dutch, the Pakistanis, the Iranians, the Macedonians, the Chinese, and the Portuguese.
The 'viertel" issue? Virtually every major city in Germany today....has a viertel (quarter) to represent some ethnic group from that city. You will have an entire neighborhood which over the past couple of decades has become the Turk-quarter, the Polish-quarter, the Albanian-quarter, the Arab-quarter, etc. Even in Wiesbaden today.....a city of 280,000 residents....a Turk-quarter is firmly into the mix of things, and there's an Arab-quarter likely in the way of building up as well. Within ten years in Wiesbaden, I'd expect a Syrian-quarter to exist, and probably an Eritrean-quarter.
There is this trend which few journalists notice or grasp. It's rare that any immigrant group appears in some rural region of Germany....or for that matter a small town of 2,000 residents. So these density regions and high immigrant targets all fall into the same circle.
At some point in the future.....I imagine some idiot will invent some new phobia word.....vietel-phobic....to indicate that some Germans are against urbanization and foreign-quarter creation. Maybe even in Berlin....the term "Ammi-phobic" will occur, to identify some phobia against too many Americans in some German urbanized area like Berlin.