This Google Street View image was sent to us by a German reader. It's quite a shocker. Unless someone at Google is playing games, which is always possible, this is an excellent UFO image.
This looks like a spot of mud that splashed up on the camera's protective dome. At least, I'm assuming the brown blob is what we're supposed to be looking at?
Moving to the right along Querstraße by clicking the ">" arrow several times, the saucer-shaped thing eventually passes in front of a building a few yards away on Querstraße. It appears to me to be a dropping on the plexiglass camera housing, or something of the sort.
Sorry, but that's bird poop. The vans that drive around doing Google street view have a dome or lexan covering the 360 degree camera, and the operator is supposed to clean and monitor it. If you move down the street, you can see the stain morph and change color in the sun.