yes the effect is amazing!
but what would these be for in real life?
They are usually used on access roads where access is no longer needed, to stop people from driving in there, say at an empty factory site, or say, near us there was an old Mercedes dealership that stood empty for a few years and these were placed at the entrance road to stop vehicles getting in.
Next door to our house we have a large yard that is no longer used, and there is one of these blocks behind the gates to stop Gyppos from getting in and setting up camp.
Here is a pic of some square ones to stop travellers getting onto this field:
Basically, to stop travellers getting in any dis-used places is a good answer
Damo