Dun Grianan Broch, Skye
As it's in an easily defended position, with good line of sight to other brochs, it's isn't difficult to understand the military strategic design behind it's construction. There isn't much left of the original broch as it has been reduced practically to its foundations, while the broch mound has been converted to a sheep pen using stone from the broch. You can make out a few details around the rubble, but not much.
I thought this one would be easy access, being right beside the road on the banks of a loch, but it turned out to be one the most difficult. It's private land and access is through people's gardens, so you will need to knock a door or two and smile nicely to get permission. On top of that, the ground is boggy around the broch and there are barbed wire fences and densely planted trees to negotiate. Might be better to simply enjoy this one from the road with binoculars.
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.