The Fairy Hills of County Antrim, Ireland

The Fae, or aes sídhe, are the fairy folk that live under fairy mounds in northern Ireland. In many Irish tales, they are said to be the remnants of the Tuatha de Danann, the mythic gods of ancient Ireland. The Tuatha de Danann retreated to the fairy mounds after their defeat by the Milesians and live there still in splendor.

 I've visited a famous fairy hill called Tiveragh in Cushendall, county Antrim. The north of Ireland has many of these mounds and there are many strange stories about them. Fairy hills are often marked by a rowan or hawthorn tree that often have a small hole allowing the wee folk entrance. Humans who go down those holes may never be seen again or worse may appear several hundred years later with all their family and friends dead and gone. 

In The Black Swans Taisie, Owen, and Gilly use a fairy mound in the Other World to find their way to the court of Queen Maeb to save Conn and the other black swans.

Joseph Noel Paton abt 1849