Crannog on Ballygawley Lough. A fortified island or perhaps a totally man made island in the lake.
<a rel="nofollow" class="external text" href="https://www.geograph.org.uk/profile/125">Bob Embleton</a>
From <a rel="nofollow" class="external text" href="https://www.geograph.org.uk/photo/241304">geograph.org.uk</a>