Broch

Finella's carles builded the Kaimes, a long line of battlements under the hills, midway a tower that was older still, a broch from the days of the Pictish men […].

The last man slid the bolt in the single low narrow door. The broch was impregnable then.

Ian's eyes rolled slowly up, as though following the rough stones of the broch upwards. 'That tower rises sixty feet from the ground,' he told me, 'and it's thirty feet in diameter, wi' three floors.'