Grianán an Aileach

Grianán an Aileach, on the main Letterkenny-Derry Road, is one of Ireland's greatest circular ring forts, with a diameter of 77 feet and walls that are 17 feet high and 13 feet thick. Sitting 750 feet above sea level, this mighty stone fort takes its name from the Irish language, "Grianán Ailigh," meaning "The stone fort of the sun." Archaeologists say that the fort itself dates from 500 BC or earlier, but the circular ramparts may go back as far back as 5,000 years ago. Considering its commanding position, it probably began as a pagan temple, but from the 5th century to the 12th century, it was the royal residence of the Ulster chieftains, the O'Neills. Although greatly ravaged in medieval times, it was partly restored in the 1870's, and is still very impressive. Open daily.