Science Snapshot 11: Mystery Letter

For the next few weeks, along with some of our usual posts, we're posting a series of  'Science Snapshots'.
Science Snapshot was really popular when we ran it last year for Science Week and this will be a continuation along the same theme.

You can see all of the snapshots so far by clicking here.

Today's image is a bit a mystery for you to solve. It's a large letter 'E' made from flat stones on a remote cliff top near Castletownshend, Co. Cork. But why is it there? What's it for? Find out here!