Watenan South Broch
This one was surprisingly difficult to find. On the map it looked as if it was impossible to miss, so I didn't take care with my planning, and didn't have a map with me. I had my phone and there was an internet connection, so I checked maps online and eventually found it. You can't really see it until you're standing in it, and even then you'd only know it was a broch if you were looking for it. You can park by the start of the loch and walk from there.
Reproduced by permission of Ordnance Survey on behalf of HMSO. © Crown Copyright. All rights reserved.
Disclaimer: Some brochs were built with military defensive purpose, and as such can be situated in extremely dangerous areas, such as on the edge of cliffs and ravines. Additionally, these are Iron Age structures, most of them in ruins, and they are extremely hazardous, with crumbling stone walls and hidden chambers. Existing walls, lintels, and passages could collapse at any time. The information here is provided free but it is your responsibility to ensure its accuracy, ensure your own safety, and acquire permissions for access where necessary. Accessing brochs is done entirely at your own risk.