Microbes made this. That is the surprising thing about stromatolites: the layered, domed structures that look like cabbages turned to stone are the fossil remains of mats of bacteria that lived in shallow water and trapped sediment, growing layer on layer. They are among the oldest evidence of life on the planet, and the rocks around the Vredefort Dome in South Africa carry some very ancient examples.
The site combines this with a basal fault plane, a surface where one layer of rock has slid over another. The two features give an unusual pairing, life at its earliest and violence at its biggest, since the dome itself is what remains of an enormous asteroid impact roughly two billion years ago. The area was inscribed as a World Heritage Site in 2005. Take the patience to look: the shapes are subtle, and a cloud passing or the angle of low sun can bring out the layers.
Riding here is easy and pleasant rather than dramatic. You are in the highveld at about fourteen hundred metres, in farm country of maize and sunflowers, with low hills and a huge sky. Tarmac roads run straight, then bend around koppies, and there is the occasional gravel stretch. Wind is regular, and afternoons in summer are often broken by sudden storms with lightning that is truly alarming, so stop and wait it out rather than push on.
For fuel, food and a bed, Potchefstroom is the closest large town, about seventeen kilometres away, with a long main street, student cafes and several petrol stations. Smaller settlements nearby may have a fuel pump, but opening hours are unreliable, so go into the country with a full tank. Much of the land is privately owned, so respect gates and fences, and ask before walking onto a farm. Spring, from September to November, with fresh grass and clear days, is a good season to go.