Six hours, on the ferry from Aberdeen to Orkney. The sea was like mud: brown mud when the sun flashes on it and turns it silver-grey, rucked up into rims by boot heels. The water gathered into a pinch and pushed backwards; the ship sighed and spat out foam.

A gannet flew alongside the ferry for a while, its head yellowed as though by accident: brushed with turmeric or aged like paper. It flew very straight and seriously, its big body close to the window, and I had a strong sense of it as a living thing, an animal, held aloft by its muscles: a thick, sweet potato double handful of bird, choosing to move through the air beside us. Beyond, someone had dropped the sun on the sea, like spilt milk. I put my head on the window.

‘There’s land,’ I said suddenly, surprising myself awake. Barely, through the darkening evening, there was land.

One little nub, and a streak like a tadpole on the top of the sea. The window was blurred by a dash of rain, but the land kept coming, in a long unspooling line. It barely broke out of the sea, this island: keeping a level just above the water. And it was so flat that if you let your eyes lose focus, it vanished back into the waves. My heart started beating in my throat. As we moved closer, the island thickened, sharp at the edge like a biscuit stamped out by a cutter, but still flat on top. I wanted to snap off a piece with my teeth and feel it on my tongue.

We went out on to the viewing deck, where men were smoking and two girls were singing with their arms around each other’s waists. And more of the islands started sliding into view: dark and rocky, green and plush, on either side of us. Between them, the ship left a broad streaked white path, vanishing off into the blue horizon.

We were staying on Mainland for the whole trip – the biggest island in the archipelago – at a youth hostel in Kirkwall. Our plan was to do everything by public transport: I hadn’t managed to pass my driving test, and my mother was less and less confident behind the wheel as the years went on. What I hadn’t anticipated was just how few buses there would be once we got to Orkney. In particular there seemed to be almost none from Kirkwall to Skara Brae, the famous Neolithic settlement on the west side of the island. When I put the journey into Google Maps, our first night in the hostel, there seemed only to be one bus, which turned straight round as soon as it arrived and left again.

We lay in our single beds, and considered the problem. ‘Another option,’ I said into the dark, staring straight up, ‘might be hiring bikes.’

‘Ah,’ my mother said, injecting the syllable with all the doubt it could hold. ‘I’m not sure about that.’

I had expected this. ‘Are you worried about the gradient? Or about staying on? It’s very flat.’

‘No, darling, it’s just that I haven’t ridden a bike for decades.’

‘They say you never forget,’ I said absently, already moving on in my mind, knowing she wouldn’t agree.

‘I don’t think it’s a good idea.’

A pause.

‘Or we could hire a car,’ I said. ‘Or take a taxi.’

‘Do we really need to go to Skara Brae?’

‘Wol –’ I sat up, exasperated, ‘yes, we do. We’ve come all this way. It would be stupid to come all the way to Orkney and not go to Skara Brae.’

‘It’s just that I’ll enjoy whatever we do. Even in the simplest walk there’s something to look at and enjoy.’

A ball of irrational wire rage was rolling into me, hard. ‘Listen, this is probably the only time in our lives we’re going to come to Orkney. It would be a waste not to go.’

‘All right. I’m just saying that I really don’t mind.’

My mother: lapsing into inertia for the price of a taxi fare, for the sake of the effort it might take to try something new. How did one live in the face of this extreme passivity? If all things were equal, what were we even doing here? Why weren’t we lying on our living-room floors, watching the dance of the dust, today and every day? I turned towards the wall and pulled the thin edges of my duvet around me.

Norse mythology is full of tales of giants living out in the wilderness. This works fine in mountainous Scandinavia, but the myths faltered when they arrived in Orkney: how could anyone believe that giants were hiding somewhere in this flat landscape? So the stories about giants on Orkney became fables about what happens when you leave yourself exposed. One night a group of giants gathered to dance and they became so caught up in the music that they failed to notice the sun rising. And as its rays lit them up, they were all turned to stone: the standing stones still visible today, tall and stark on the silent fields of Orkney.

There are two major groups of standing stones on Mainland: the Stones of Stenness and the bigger Ring of Brodgar. As it happened, I’d been to see Stonehenge, their more famous southern cousin, the week before: on a bus packed with tourists, with plastic orange headphones which plugged into the seat in front of you. You could only see the henge from a distance, through a crowd of picnickers, while the rooks perched on the lintel stones and squirted white trails down the sides.

The Stones of Stenness were even older than Stonehenge. We made the trip out to see them on our first day, after we’d finished in the chapel. From the bus they were a small gathering of shards, fanning impossibly upwards from the surface of the earth. When we arrived there was no one else there. No fence or barricade or ticket booth. Just some sheep, staring mildly, and a folding blackboard advertising a free guided tour at 10 a.m. And beyond, a sky ridged with dark grey.

The grey stones stood like huge, gentle, awkward men, wide-shouldered, hunching round slightly, who had lost their arms somewhere. Three tall ones, and a jaunty small one which changed direction halfway along its length, bending the other way to make a corner. One of the myths which hangs over Orkney is that the standing stones leave their places at Hogmanay and go down to the loch to drink. I could see, in my mind, the kind, worried stones twisting their big shoulders right down, with great difficulty, to try to get their mouths to the water level for a sip.

I walked up to the first standing stone. My mother had found a bird to look at in the nearby loch and hadn’t caught up yet. The stones were pitted with the acid of rain, their pockets full of yellow lichen, right to the top, far over my head. I put my face against the cold dry surface and closed my eyes. From the side this stone was almost fragile, its layers worn unevenly away. As though it only kept standing through great effort, on the green field which stretched away in all directions, for thousands of years.

Another stone lay flat on the ground, with smaller stones balanced upright nearby. The quiet was complete. Little wisps of sheep wool had caught in the cracks and scars of the rock: they fluttered in the wind. Outside the stone field, the grass flowed and rippled, shining like clean hair.

What are Britain’s stone circles for? They were used for ritual purposes. That’s an old archaeologist’s joke. If you don’t know what a monument or artefact was for, you say: it had ritual purposes. Looking at my mother’s Orkney guidebook, though, I kept thinking of a tweet I’d seen, saying that if an archaeologist dug up Disneyland, they would without hesitation classify it as a religious site. We use such poor, narrow, clumsy categories to try to grasp the unknown. Difference is difficult to truly imagine. Who says that the stone circles were even monuments at all? The archaeologist Colin Richards suggests: ‘Rather than being built solely as ritual or ceremonial centres it may have been the actual acts of construction that provided the main social focus.’ People would have gathered to watch and participate, with stones perhaps being added slowly over time. Perhaps it was the type of stones that mattered: maybe they were from a sacred place. Perhaps the point was not a symbolic ring to unify society, but a competitive process of quarrying and transportation.

It’s one mental step to establish that people in the past – or in other countries – were or are ‘just like us’. That’s an easy act of generosity which is really more like narcissism. It’s quite another thing to grasp that their thinking, their priorities, their assumptions, might be utterly different from ours: unimaginable and unreachable. And yet at the same time – this is the leap – to understand viscerally that they were still just as human. Our own minds are not the measure of what is worthwhile.

Despite its general flatness, many strange mounds dot the Orkney landscape. Some of these are natural glacial deposits. Some are artificial: covering Neolithic chambered tombs, or Iron Age ‘brochs’: magnificent stone roundhouses. Fairies are said to live in these mounds, with the power to steal your babies or your horses if you disturb them.

At Skara Brae, when we finally got there, ten perfectly preserved neolithic dwellings sank into the ground, each with the same furniture: two bed boxes, made out of propped-up stones, and a stone dresser. The grass made figures-of-eight atop the stacked stone walls, each house nesting into its neighbour: they had no roofs, and you could look straight down from above into the neat, tight living quarters. But the seventh house was just a brown mound, scattered with tufts of grass.

House 7 contains the best preserved stone carvings found at Skara Brae. It was fitted in 1929 with a shielding glass roof, but studies revealed that this was creating temperature changes that caused the carvings to flake and crumble. In 2005 the decision was made to re-roof the building in turf.

I stared at the blank brown mound for a long time, before I moved on to the other dwellings. In the grass, by every house entrance, small signs read no admittance. This far: no further. Under the hot blue sky, the green fields stretched far and flat around us.

Image © Tom Wachtel