I have only a little experience building stone walls (and it is a lot harder than it looks!!) but I can see mortar in the left side of the image so perhaps the wall was build to have the appearance of a dry stone wall.
The garden and the wall belong to Spencer Barrett of the University of Toronto.
Check this link to find the contact email for Mr Barrett; if you attach the photo to an email he may offer more assistance:
http://www.bgci.org/garden.php...
