Kilchurn Castle was abandoned after it was struck by lightning in 1760 and is now cared for by Historic Environment Scotland. It is a picture postcard ruin often seen in photographs of Loch Awe with Ben Cruachan behind and can be seen from the road on the other side of the loch while travelling north.
You can however walk right up and around it. Park in the little parking area just off the A85 and walk all the way out to the Castle. It was built by Sir Colin Campbell, 1st Lord of Glenorchy in the early 15th century and has been a fortress, a family home and a garrison stronghold with barracks in the courtyard.
These barracks are still there and are in fact the oldest surviving in Britain.