This is a lake, so not a prehistoric monument, but the story is so good and the location still ancient that I had to include it. Welsh fairy stories are some of the best there are, it wouldn't be complete without this most famous fairy story. From The Welsh Fairy Book, by W. Jenkyn Thomas, 1907:
High up in a hollow of the Black Mountains of South Wales is a lonely sheet of water called Llyny Fan Fach.
In a farm not far from this lake there lived in the olden time a widow, with an only son whose name was Gwyn. When this son grew up, he was often sent by his mother to look after the cattle grazing. The place where the sweetest food was to be found was near the lake, and it was thither that the mild-eyed beasts wandered whenever they had their will. One day when Gwyn was walking along the banks of the mere, watching the kine cropping the short grass, he was astonished to see a lady standing in the clear smooth water, some distance from the land.
She was the most beautiful creature that he had ever set eyes upon, and she was combing her long hair with a golden comb, the unruffled surface of the lake serving her as a mirror.
He stood on the brink, gazing fixedly at the maiden, and straightway knew that he loved her. As he gazed, he unconsciously held out to her the barley-bread and cheese which his mother had given him before he left home. The lady gradually glided towards him, but shook her head as he continued to hold out his hand, and saying:
Cras dy fara, O thou of the crimped bread,
Nid hawdd fy nala, It is not easy to catch me,
she dived under the water, and disappeared from his sight.
He went home, full of sorrow, and told his mother of the beautiful vision which he had seen. As they pondered over the strange words used by the mysterious lady before she plunged out of sight, they came to the conclusion that there must have been some spell connected with the hard-baked bread, and the mother advised her son to take with him some "toes," or unbaked dough, when next he went to the lake.
Next morning, long before the sun appeared above the crest of the mountain, Gwyn was by the lake with the dough in his hand, anxiously waiting for the Lady of the Lake to appear above the surface. The sun rose, scattering with his powerful beams the mists which veiled the high ridges around, and mounted high in the heavens. Hour after hour the youth watched the waters, but hour after hour there was nothing to be seen except the ripples raised by the breeze and the sunbeams dancing upon them. By the late afternoon despair had crept over the watcher, and he was on the point of turning his footsteps homeward when to his intense delight the lady again appeared above the sunlit ripples. She seemed even more beautiful than before, and Gwyn, forgetting in admiration of her fairness all that he had carefully prepared to say, could only hold out his hand, offering to her the dough. She refused the gift with a shake of the head as before, adding the words:
Llaith dy fara, O thou of the moist bread,
Ti ni fynna. I will not have thee.
Then she vanished under the water, but before she sank out of sight, she smiled upon the youth so sweetly and so graciously that his heart became fuller than ever of love. As he walked home slowly and sadly, the remembrance of her smile consoled him and awakened the hope that when next she appeared she would not refuse his gift. He told his mother what had happened, and she advised him, inasmuch as the lady had refused both hard-baked and unbaked bread, to take with him next time bread that was half-baked.
That night he did not sleep a wink, and long before the first twilight he was walking the margin of the lake with half-baked bread in his hand, watching its smooth surface even more impatiently than the day before.
The sun rose and the rain came, but the youth. heeded nothing as he eagerly strained his gaze over the water. Morning wore to afternoon, and afternoon to evening, but nothing met the eyes of the anxious watcher but the waves and the myriad dimples made in them by the rain.
The shades of night began to fall, and Gwyn was about to depart in sore disappointment, when, casting a last farewell look over the lake, he beheld some cows walking on its surface. The sight of these beasts made him hope that they would be followed by the Lady of the Lake, and, sure enough, before long the maiden emerged from the water. She seemed lovelier than ever, and Gwyn was almost beside himself with joy at her appearance. His rapture increased when he saw that she was gradually approaching the land, and he rushed into the water to meet her, holding out the half-baked bread in his hand. She, smiling, took his gift, and allowed him to lead her to dry land. Her beauty dazzled him, and for some time he could do nothing but gaze upon her. And as he gazed upon her he saw that the sandal on her right foot was tied in a peculiar manner. She smiled so graciously upon him that he at last recovered his speech and said, "Lady, I love you more than all the world besides and want you to be my wife."
She would not consent at first. He pleaded, however, so earnestly that she at last promised to be his bride, but only on the following condition. "I will wed you," she said, "and I will live with you until I receive from you three blows without a cause - tri ergyd diachos. When you strike me the third causeless blow I will leave you for ever."
He was protesting that he would rather cut off his hand than employ it in such a way, when she suddenly darted from him and dived into the lake. His grief and disappointment was so sore that he determined to put an end to his life by casting himself headlong into the deepest water of the lake. He rushed to the top of a great rock overhanging the water, and was on the point of jumping in when he heard a loud voice saying, "Forbear, rash youth, and come hither."
He turned and beheld on the shore of the lake some distance from the rock a hoary-headed old man of majestic mien, accompanied by two maidens. He descended from the rock in fear and trembling, and the old man addressed him in comforting accents.
"Mortal, thou wishest to wed one of these my daughters. I will consent to the union if thou wilt point out to me the one thou lovest."
Gwyn gazed upon the two maidens, but they were so exactly similar in stature, apparel and beauty that he could not see the slightest difference between them. They were such perfect counterparts of each other that it seemed quite impossible to say which of them had promised to be his bride, and the thought that if perchance he fixed upon the wrong one all would be for ever lost nearly drove him to distraction. He was almost giving up the task in despair when one of the two maidens very quietly thrust her foot slightly forward. The motion, simple as it was, did not escape the attention of the youth, and looking down he saw the peculiar shoe-tie which he had observed on the sandal of the maiden who had accepted his half-baked bread. He went forward and boldly took hold of her hand.
"Thou hast chosen rightly," said the old man, "be to her a kind and loving husband, and I will give her as a dowry as many sheep, cattle; goats, swine and horses as she can count of each without drawing in her breath. But remember, if thou strikest her three causeless blows, she shall return to me."
Gwyn was overjoyed, and again protested that he would rather lop off all his limbs than do such a thing. The old man smiled, and turning to his daughter desired her to count the number of sheep she wished to have. She began to count by fives - one, two, three, four, five - one, two, three, four, five - one, two, three, four, five - as many times as she could until her breath was exhausted. In an instant as many sheep as she had counted emerged from the water. Then the father asked her to count the cattle she desired. One, two, three, four, five - one, two, three, four, five - one, two, three, four, five - she went on counting until she had to draw in her breath again. Without delay, black cattle to the number she had been able to reach came, lowing out of the mere. In the same way she counted the goats, swine and horses she wanted, and the full tale of each kind ranged themselves alongside the sheep and cattle. Then the old man and his other daughter vanished.
The Lady of the Lake and Gwyn were married amid great rejoicing, and took up their home at a farm named Esgair Llaethdy, where they lived for many years. They were as happy as happy can be, everything prospered with them, and three sons were born to them.
When the eldest boy was seven years old, there was a wedding some distance away, to which Nelferch - for that was the name the Lady of the Lake gave herself - and her husband were specially invited. When the day came, the two started and were walking through a field in which some of their horses were grazing, when Nelferch said that the distance was too great for her to walk and she would rather not go. "We must go," said her husband, "and if you do not like to walk, you can ride one of these horses. Do you catch one of them while I go back to the house for the saddle and bridle."
"I will," she said. "At the same time bring me my gloves. I have forgotten them - they are on the table."
He went back to the house, and when he returned with the saddle and bridle and gloves, he found to his surprise that she had not stirred from the spot where he had left her. Pointing to the horses, he playfully flicked her with the gloves and said, "Go, go (dos, dos)."
"This is the first causeless blow," she said with a sigh, and reminded him of the condition upon which she had married him, a condition which he had almost forgotten.
Many years after, they were both at a christening. When all the guests were full of mirth and hilarity, Nelferch suddenly burst into tears and sobbed piteously. Gwyn tapped her on the shoulder and asked her why she wept. "I weep," she said, "because this poor innocent babe is so weak and frail that it will have no joy in this world. Pain and suffering will fill all the days of its brief stay on earth, and in the agony of torture will it depart this life. And, husband, thou hast struck me the second causeless blow."
After this, Gwyn was on his guard day and night not to do anything which could be regarded as a breach of their marriage covenant. He was so happy in the love of Nellerch and his children that he knew his heart would break if through some accident he gave the last and only blow which would take his dear wife from him. Some time after, the babe whose christening they had attended, after a short life of pain and suffering, died in agony, as Nelferch had foretold. Gwyn and the Lady of the Lake went to the funeral, and in the midst of the mourning and grief, Nelferch laughed merrily, causing all to stare at her in astonishment. Her husband was so shocked at her high spirits on so sad an occasion, that he touched her, saying, "Hush, wife, why dost thou laugh?"
"I laugh," she replied, "because the poor babe is at last happy and free from pain and suffering." Then rising she said, "The last blow has been struck. Farewell."
She started off immediately towards Esgair Llaethdy, and when she arrived home, she called her cattle and other stock together, each by name. The cattle she called thus:
Mu wlfrech, moelfrech, Brindled cow, bold freckled,
Mu olfrech, gwynfrech, Spotted cow, white speckled;
Pedair cae tonn-frech, Ye four field sward mottled.
Yr hen wynebwen, The old white-faced,
A'r las Geigen, And the grey Geigen
Gyda'r tarw gwyn With the white bull
O lys y Brenin, From the court of the King,
A'r llo du bach, And thou little black calf,
Sydd ar y bach, Suspended on the hook,
Dere dithe, yn iach adre! Come thou also, whole again, home.
They all immediately obeyed the summons of their mistress. The little black calf, although it had been killed, came to life again, and descending from the hook, walked off with the rest of the cattle, sheep, goats, swine and horses at the command of the Lady of the Lake.
It was the spring of the year, and there were four oxen ploughing in one of the fields. To these she cried:
Y pedwar eidion glas, Ye four grey oxen,
Sydd ar y ma's, That are on the field,
Deuweh chwithe Come you also
Yn iach adre! Whole and well home!
Away went the whole of the live stock with the Lady across the mountain to the lake from whence they had come, and disappeared beneath its waters. The only trace they left was the furrow made by the plough which the oxen drew after them into the lake; this remains to this day.
Gwyn's heart was broken. He followed his wife to the lake, crushed with woe, and put an end to his misery by plunging into the depths of the cold water. The three sons distracted with grief, almost followed their father's example, and spent most of their days wandering about the lake in the hope of seeing their lost mother once more. Their love was at last rewarded, for one day Nelferch appeared suddenly to them.
She told them that their mission on earth was to relieve the pain and misery of mankind. She took them to a place which is still called the Physician's Dingle (Pant y Meddygon), where she showed them the virtues of the plants and herbs which grew there, and taught them the art of healing.
Profiting by their mother's instruction, they became the most skilful physicians in the land. Rhys Grug, Lord of Llandovery and Dynevor Castles, gave them rank, lands and privileges at Myddfai for their maintenance in the practice of their art and for the healing and benefit of those who should seek their help. The fame of the Physicians of Myddfai was established' over the whole of Wales, and continued for centuries among their descendants.