This is a place that stretches the imagination. As we enter the Tankwa, we come upon a science fiction scene - fields of red grass. The whole family stop to get out of the car, to examine the seaweedy little strands of the stuff.
Three days later, when we're travelling home through the driest part of the park, the landscape is so arid, it robs us even of conversation. Yet when we are in the park, the huge landscape makes us strangely elated, striking some deep chord - perhaps in our DNA, I muse. After all, did our hunter-gatherer ancestors not roam plains as huge as these, soaking up the size of them?
We've come to the Tankwa upon the invitation of our friend Curt Warrin, a member of the Boland Honorary Rangers group of volunteers who work in the park on several weekends a year. "We love it. There's nothing there," Curt had told us weeks previously, grinning as if he was issuing an irresistible invitation. The reverse psychology worked; our curiosity was aroused.
However, Curt did also say the flowers were better than on the West Coast this year, and he may have been right. From the house where we are staying with the Honorary Rangers, the flat plains are awash with yellow, white and purple daisies. There is a dramatic edge to this prettiness. The flowery plains stretch off to a ring of mountains so steep that they cast shadows even in the midday sun.
The Tankwa Karoo National Park was declared in 1986, and SanParks has been buying more farms to increase its size ever since. It is now the fourth-biggest park in the country. Vast and dry, it is full of surprises, as well as stories, if only you know who to ask. We were lucky. We had Bev and Rina.
Part of the Honorary Rangers group, Bev and Rina are collecting the stories of the previous farm dwellers of the area. Their work is at too early a stage to make public, but they show us moving photographs showing what life was once like.
The abandoned farmhouses and shepherd's house are simple dwellings, some built of mud and chaff, the roofs thatched with wheat - explaining, to some degree, why the houses eroded so quickly.
It was a local custom to buy a coffin long before you died to spare others the expense, and one or two of the abandoned dwellings still have the coffin shelved up against a wall.
The Honorary Rangers, working from several vicinities in Cape Town, are groups of volunteers who adopt a park and raise funds, create public awareness and even supply the manpower to build facilities at the park. Without them, parks would be far worse off and, in some areas, would struggle to survive.
It's no cinch becoming one: to qualify, applicants must pass an orientation course, a communication and personal interaction course, and actively participate in the group's activities. This is volunteerism with stripes. And this weekend they are laying bricks and shovelling concrete to build an ablution block.
The Honorary Rangers hint that even the plants here have characters. The succulent bushes covering tracts of the plains are called melkvingers (milk fingers) and might well have white sap, although we didn't stop to test; the highly poisonous gifbol (poison ball) has a flamboyant fan of green leaves; the hedgehog bush is a ball of brown spikes, and then there is hoodia gordonia, which the Khoisan used to quell their hunger when food was short. These days it's a slimming aid, and poachers are coming into the park, even by helicopter, to take the plants and sell them in America to be turned into slimming aids. It's a serious conservation problem.
The Gannaga Pass, which winds up the mountains north of the house, was built during the Great Depression as a job creation project. We drive up the hairpin bends, the drop on the driver's side horribly sheer. At the top is another surprise, the Gannaga Lodge.
This is a low-slung building of mud and stone, with absurdly dramatic views from its stoep of Karoo mountains and the drop down to the valley below. A cheerful man is stacking furniture, and the place is pounding with pop music.
The managers tells us there was a wedding this morning and they are clearing up. He invites us for tea, but we cannot handle the beat and leave. Later, the Honorary Rangers tell us that the place is a popular wedding venue. It's a fantastic place for any function, but so remote that I conclude that the people who get married there are doing their utmost to put guests off and have a small wedding. Or perhaps I'm just ignorant of how Karoo towns work: the lodge is on the way to Middelpos, after all.
Later, Bev tells a tale relating to the town. A herd of feral goats with long hair has been living in the Langkloof for about 60 years, she says. There are between 300 and 1 000 of them, depending on who is telling the story. Why have they not been caught? "Because when anyone tries, they just run off to Middelpos," she says, laughing uproariously. "Everything goes to Middelpos."
When we leave the Gannaga Lodge we take the road that may well lead to Middelpos, but it seems to stretch on forever, so we take a side road - which becomes so rocky that when I get out and walk, I quickly leave the car behind. After a few minutes eerily alone on this high Karoo road, I go to the mountain edge and find myself looking down into a huge plunge into the Langkloof - 1 000 metres down, we are later told.
This isn't just a drop, it's a canyon. The slope beneath me is so sheer, I can't see it, and the mountain opposite so steep and dry that not even the Karoo succulents cling to it. There is only scree, waiting perilously to fall. And far beneath me, a world away, is a tiny riverbed green with trees, meandering down into the distance and forking off into another faraway kloof.
Baboons are barking a little way off and the odd bee buzzes around my legs, but otherwise there is such a deep silence, I might have been the first person here. It's not an uncommon feeling in the Tankwa. Perhaps that's what made Curt smile as he invited us to the place where "there's nothing there".