When Diana Gabaldon wrote Outlander she had NOT been to Scotland. So, Craigh na Dun is fictional. Not based on an actual stone circle. Ms Gabaldon made it up. This does not detract from the wonder of visiting actual stone circles. I just got back from a wonderful trip to the UK and visited many circles. They are amazing.
There is an excellent book on stone circles by Aubrey Burl - I am pretty sure you can get it on Amazon. It gives good directions to them so if you are planning a stone circle tour, I really recommend this book! Even if you are not, it is a great reference book. Has black and white pictures of many of the circles. It covers Britian, Ireland and Brittany.
Something is not right. This message is just to keep things from messing up down the road