I suppose it depends on whether you believe in fairies. In Ireland, the fairy folk are known by the term Aos Sídhe (pronounced kind of like Es-Shee). According to stories contained in early texts and manuscripts like the eleventh-century Lebor Gabála Érenn, also known as 'The Book of Invasions', the Sidhe are the descendants of the Tuatha de Danann, a magical race of supernatural beings who once ruled Ireland, but were driven below ground by the trickery of an invading mortal race, known as the Milesians. The Sidhe very much have a presence in Ireland's landscape, literature, and psyche, even today, but they are as unlike the winged Tinker-Bell trope as you can get!
Early Irish literature is littered with references to the Danann and the Sidhe living in fairy mounds, or that the mounds were gateways to the Otherworld where they lived. However, the magical realm could also be accessed through water, by passing the seventh wave, by sailing west, and by descending through a magical door among the roots of a fairy tree. In many ways, the Otherworld seems to function as an alternative or parallel universe in which Sidhe and mortal co-existed side by side, and through which they could interact.
So, where does this idea of the mound as a magic portal to the Otherworld come from? Well, right back to that story of the Danann being tricked by the Milesians. Basically, the story goes that when the Danann were defeated in battle, the two races agreed to share rulership of the land. The Milesians chose to rule that half of Ireland which lay above the ground, leaving the Danann to rule that which lay below.
If you want to read my version of this story, and others, click the image to download a copy of Conor Kelly's Legends of Ireland, available FREE until the end of June 2020.
However, the magical realm was no Underworld. In the literature it is described as a place of beauty much like the Ireland we know, only better, and all who inhabit this world are beautiful, ever-young, strong and long-lived; it is a land of plenty where no one suffers. Mortals are sometimes invited in, but it comes at a price; Oisin, son of hero Fionn mac Cumhaill, for example, thought he had only lived there for three years with his Sidhe lover, Niamh of the Golden Hair, but found out on his return to Ireland that three hundred years had passed.
Fionn mac Cumaill himself had a few strange encounters with Sidhe mounds. In 'The Chase of Síd na mBan Finn', the Fianna, after three days of unsuccessful hunting, gather on a hill which Fionn tells them is the burial mound of his relative, Failbhe Finnmaísech. Here, he mysteriously receives knowledge that his hunt will only be successful if the Fianna goes after the giant boar named Formael which had killed Failbhe.
So, although Fionn magically receives knowledge on this mound, it is clearly described as a burial mound, and not an entrance to the Otherworld, and this is confirmed later in the story when the Fianna build burial mounds for their fallen friends, killed by the boar.
However, Fionn's mother is Muirne of the Swan Neck, and she is a woman of the Tuatha de Danann. It is not clear in this story whether Failbhe is related to Fionn through his mortal father, or his Danann mother. There are echoes also of dream incubation here, a form of divination obtained by sleeping in the grave of one's ancestors; for example, Muirgen, son of sixth century poet, Senchán Torpéist, was said to have learned the full story of the Ulster tale, 'The Cattle Raid of Cooley' from the ghost of Fergus mac Róith by sleeping in his grave.
You can read more about this in my post, The Aisling: Not so Sweet Dreams.
In the story of Cael and Credhe, Fionn goes to the Sidhe King of Ciarraighe Luachra seeking the hand of his daughter, Credhe, for one of his men, Cael; here, the mound is most definitely described as an entrance to the Otherworld:
'they came to the door of the hill of the Sidhe and knocked at it with the shafts of their long gold-socketed spears.'
Stories of fairies and fairy mounds have endured in the folklore handed down through the centuries. For example, four mounds in Mullanasole, Co. Donegal, were described thus:
People have seen lights about these mounds and in bad weather when everything and everywhere is soaked in rain and dirt these mounds are never wet. And it was noticed that whenever there was a snow-storm these mounds were quite green when every other place was white with snow.
It is thought that falling asleep on a fairy mound could lead to abduction by the Sidhe. Turlough O'Carolan, a harper in the eighteenth century, was said to have been gifted his musical skills after falling asleep on a fairy mound.
There is a story associated with a mound known as Knockgrafton, near Limerick, in which a humped man named Lusmore fell asleep and was invited into the mound to dance and sing with the Sidhe that lived there. They liked him so much, they removed his hump and sent him on his way. People came from far and wide to see this miracle, including another man with a humped back. Lusmore felt so sorry for him, he confided his secret. This man went straight to the mound expecting a similar cure, but the Sidhe gave him an extra hump instead for his impertinence.
This theme of mischief after falling asleep on a mound is a common one, and features in Christian myths, too. In 'The Abbot of Druimenaig', the said abbot falls asleep on a 'big, high pleasant hill' after preparing a feast for Easter. When he awakes, he finds he has mysteriously transformed into a woman:
'And this is how he was, the skirt of a woman's tunic on him down to the ground, and on his head there was a woman's hairdo, long golden very beautiful hair falling in fine curls from the top of his head, and when he passed his hand over his face he did not find any hair of a beard or moustache there, and he put his hand between his thighs and he found the sign of womanhood there.'
As a woman, the abbot goes on to marry a man and bears him seven children in the space of seven years. On the seventh Easter, she falls asleep on the same hill, only to find herself transformed back into a man. He went back to his own wife (yes, the abbot was married) but no one believed his story. He was distraught over losing the children he had borne as a woman. Eventually, he convinces everyone, finds the man he was married to, and a judgement is made that they share the children between them.
Barbara Hillers, in her journal article, 'The Abbot of Druimenaig: Gender-Bending in Gaelic Tradition', claims this story has 'its roots in oral fairy legend' and has probably 'been known in Ireland for at least half a millennium'. Falling asleep on a fairy hill at a sacred time of year after sunset is, she writes, 'asking for trouble'; the abbot did not recognise that he was transgressing across the threshold to the Otherworld, and as such, received his punishment.
Whilst the turn of events seems strange to us, this story teaches many lessons about acceptable behaviour for men and women in medieval society, when many people were illiterate and learned instead from the oral tradition, and provides a fascinating insight for today's scholars.
Of course, archaeology has revealed that these graceful formations in the landscape were in fact burial mounds, in which bone fragments and ashes along with some evidence of grave goods have been found. Yet the legends still persist, and there aren't many people who would be foolish enough to risk a night on a burial mound, even today.