The buildings are the remains of a C19th coastal battery and firing range. These are depicted on the 2nd edition of the OS 6-inch map dating from 1903 http://canmore.rcahms.gov.uk/en/site/311761/details/birsay+point+of+snusan/
Uploaded to Geograph by Andrew Curtis on 13 August 2012
Photo © Andrew Curtis, 13 August 2012.
Licensed for reuse under this Creative Commons licence