Backyard mosques are a typical German phenomenon. Muslim communities need(ed) to (anyone knows any further?) register as clubs/associations ("Verein"). The mosques run by the "Moscheevereine" are barely visible from the outside. In this case, there is no printed sign on the outside of the building complex as usual. The Turkish word for mosque has been painted and in technical lettering to be precise. This is to my great surprise but then it goes along with functionality often found in German backyard mosques. Also, I have found a simiar case of technical lettering of the word "mosque" in Arabic in Morocco.

During the last years some changes in Germany (which need to be specified...) have lead to more visibility of Islamic architecture in the public realm - not undisputedly though.