The picture was taken in Southwest Germany in June, and they covered the ground of a garden we were at...
I am almost sure this is Sedum reflexum (aka S. rupestre), in English prickmadam or crooked yellow stonecrop and in German Felsen-Mauerpfeffer. It usually grows at rocky or stony ground, not full of grass.
Distinctive features are the pointed leaves, which are not as round as in S. album and also the bended stem (flower stalks are always bend, hence the name reflexum). Its' flowers should be yellow.
These features can be seen well at the botanical drawing below (from wikipedia commons).
The reason I'm not completely sure is that in garden (and on roofs) exotic sedums are often planted.