After I die, I want my ashes to be scattered in Pentre Ifan’s shadow. The scatterer will have to wait for a rare, windless day. It’s on those still days that the nearby hawthorn trees, the ones most exposed and bent nearly lateral by prevailing westerlies, can break your heart. They look ridiculous, like blown birthday candles perpetually being extinguished, gusted over to one side. When there’s no wind, you wonder why they don’t spring back up straight. But they never do. The hawthorns grow at a respectful distance to the west of Pentre Ifan. The horizon behind them is hitched to the sky by the largest “mountain” in west Wales: Carn Ingli, the Hill of Angels. It’s just 347 metres of ancient shield volcano, but it has a big reputation. They say if you sleep on its summit, angels will whisper their secrets in your dreams. Another version says the Earth will speak to you as you sleep. I’d rather hear what the bedrock has to say. Wales’ first national poet, Gwyneth Lewis, declares in six-foot letters on the slate facade of Cardiff’s Millennium Centre: “In these stones, horizons sing.” I’m American, but I’ve been listening to Welsh rock for well over 30 years. I first went to Wales as a graduate student in Lampeter, and felt instantly at home in the landscape. Friendships, familiarity with history, legend, even language, all came later, but the West Walian landscape sang to me immediately of belonging. The countryside seemed both familiar and important, even though I’d never been there before. Its hilly, treeless lucidity revealed how the earth had been made, by both men and glaciers. I felt I’d found the key to a map I’d carried in my head since I was a little girl, but because I’d always lived in cluttered places, had never been able to read. And until I could read that map, I’d had no sense of my or my species place on the planet. That’s how important Wales was for me – and I’m just describing the reactions of my first month! The highlight of my first month was a visit to Pentre Ifan in Pembrokeshire’s Preseli Hills. Pentre Ifan is a megalithic monument, which just means it’s a structure made of big rocks: six standing stones and a massive, horizontal capstone. The latter is delicately balanced more than two metres up in the air atop just three of the vertical stones – a fourth barely misses touching. The effect is of a laden tray carried on the fingertips instead of the palm of the hand. One of the remaining standing stones serves as a stationary door, and the other two huddle nearby in moral support. All are covered in generations of lichen that bristle atop one another, grey-on-grey, like big, dirty snowflakes. Pentre Ifan may also be called a cromlech, a prehistoric tomb, or a dolmen. It was built about 5,500 years ago, 1,000 years before the Egyptians started work on the pyramids at Giza. Wales’s “ancient” castles are just pop-up ruins by comparison. I live in the US but come to Wales every year to direct the Dylan Thomas Summer School creative writing programme. We often take the students to Pentre Ifan, no matter the weather. Perhaps because of its singularity, and the fact that I live most of my life elsewhere, the monument acts like a lightning rod to memory. I see the students photographing the dolmen, but I also see myself at 23, flirting with the young archaeologist who first took me there. Blink. I see myself at 30 with a different haircut and my now-longtime female partner, pretending the capstone is falling on my head. Blink. I see myself alone at 56, talking on the phone to my 95-year-old mother in the US, reminding her who I am. How about this: what if Pentre Ifan was originally built as a lightning rod to memory, exactly the way it still works for me today? Archaeologists have long thought of portal dolmens as tombs, though no trace of human remains has ever been discovered at Pentre Ifan. In Places of Special Virtue, their 2004 study of megaliths and the neolithic landscape of Wales, Vicki Cummings and Alasdair Whittle propose a different theory about Welsh megaliths in particular. What if portal dolmens such as Pentre Ifan were bookmarks in an origins story gleaned from the landscape? Comparing the settings of 104 monuments in Wales, Cummings and Whittle discovered that megaliths such as Pentre Ifan are geographic cruxes. From each a viewer can take in a range of distinctive landscape elements. Don’t think of Pentre Ifan as an end in itself, they say; think of it instead as a prompt to look out rather than in. A giant picture frame that draws together views of the Irish Sea, Carn Ingli, the Preseli Hills, and four rocky outcrops on the south-western horizon called Meibion Owen – Owen’s Sons. The Welsh landscape would have been more forested in Neolithic times, but these landmarks would’ve been visible through the trees, especially in winter. A radical idea, right? And why not? Cummings and Whittle suggest that in neolithic Wales, clans weren’t settled; they migrated seasonally, and dolmens such as Pentre Ifan acted as mnemonics for their storytellers, prompting tales about places and past. No one can be certain as to the megaliths’ purpose – that horizon of forgetting has disappeared over the rim of prehistory – but I believe this theory. In fact, I can enact it for you. If you stand to the east and look through Pentre Ifan’s great aperture, you’ll see Carn Ingli framed in the westward distance. I suggest hiking it – an hour up, a picnic, 45 minutes down. It offers a wonderful view of Cardigan Bay, and in certain weather, you’ll see sunbeams bent into rings around its summit as they refract in the mist. The fires of the gods of old. If you stand at the dolmen and gaze north, the Earth slopes down to form the great bowl of the Nevern valley, crowned by the blue blur of the bay. On the A487, nearly opposite the Pentre Ifan turning, is a signpost to Nevern/ Nanhyfer. I love the name in both languages. Nevern. It’s both promise and prohibition. “This way to never.” Go that way. You’ll come to a twilight of ancient yews – about 500 years old and famous for their blood-red sap – and just past them, in a churchyard, a 10th-century Celtic cross nearly four metres tall and swathed in neon-orange lichen. Then you’ll come to Saint Brynach’s church, founded in about 540, though the oldest element of the current structure is its 14th-century tower. I like to spend a quiet moment or two inside, my fingers tracing the Ogham inscriptions – its letters like rain slashes in children’s drawings – of a gravestone of the Romano-British worthy, Maglocunus, set into the sill of the south window. If you return to Pentre Ifan and turn east, you’ll be looking in the direction of Castell Henllys, an evocative reconstructed iron age village. And if you gaze south, you’ll see the Preseli Hills, original home of Stonehenge’s bluestones, riding earthen waves to the horizon. The Preselis offer some of the best hiking in Wales. My favourite trail is the seven-mile Golden Road, a 4,000-year-old ridgeway frequented by hikers and wild ponies, which extends between Crymych in the east and the Gwaun Valley in the west. Tradition has it that gold mined in Ireland’s Wicklow Hills was transported in prehistoric times via this route to England. When I last hiked it with friends from Swansea, their daughter Roísín declared it “The Main Street” of her Neolithic ancestors. At the centre of this compass is Pentre Ifan itself, my favourite place on Earth. Because I don’t live in Wales, I often feel hiraeth for the rootedness I sense in its presence – a chain of associations taking me back through my own past all the way to the stone age. Hiraeth is an untranslatable Welsh word meaning something like longing, or homesickness. I like to think of it as an acute presence of absence haunting the present moment. Over the past nine years I’ve been writing a memoir called The Long Field, which uses hiraeth as a lens to view Wales and my own life. In the book I say that I believe hiraeth is at the heart of Welsh culture. I don’t just mean that Wales has suffered many losses and absences; I mean that absence often becomes an engine for creative invention as well. Case in point: megaliths such as Pentre Ifan are monuments orphaned by time. Their meaning is absent to us now. And yet, that missing signification prompts archaeologists like Cummings and Whittle to wonder and, through their research, reimagine the past. It also prompts all sorts of folk tales to grow up around the monuments. At Pentre Ifan, the tradition is to make a wish beneath the capstone’s southern overhang. My wish is that we never solve the riddle of the megaliths. I never want to stop wondering. Pamela Petro’s The Long Field is out now (Little Toller Books, £20). To buy a copy for £17.40 including UK p&p, go to guardianbookshop.com Three more ancient sites in Wales Carreg Samson A 5,000-year-old neolithic chambered tomb on a magnificent clifftop overlooking the sea in Pembrokeshire. Legend holds that Saint Samson set the capstone in place with his little finger. Foel Eryr Cairn A short walk from the western trail head of the neolithic Golden Road, is this large, conical bronze age burial site with a commanding presence and superb views. Have a look, then double back and walk the ancient road. Bryn Celli Ddu This megalithic monument on Anglesey is the most famous on my list, and is a superb passage tomb. It is all the more exceptional because it’s still covered in a grassy mound. It’s wonderfully eerie inside, and its passage is roughly aligned with the summer solstice.