Built sometime around the year A.D. 950, this rugged early medieval ring fort was used as a defensive structure for at least 200 years. It’s one of the best-preserved ruins of its kind in Ireland; the dry stone walls are around 3m (9 3/4 ft.) tall in places, and equally as thick. Today it’s partly under the care of an archaeology school, so you’ll often see students at work. A visitor center has a cafe and an exhibition focusing on the Burren’s forts, dolmens, and other ancient monuments. More entertainingly, you can also see sheepdog demonstrations at the fort from March to October; visit the website to find out when.