Dun Carloway Broch

 
 

The Hebrides and also Shetland and Orkney have these great little castles called Broches.  They are round tower houses built entirely without mortar, with a stair in the wall thickness to the upper stories.  The title “Dun” also means “fortified place”, and I think “Broch” refers specifically to the round tower.

Dun Carloway Broch