Two billion years ago, give or take, something the size of a mountain hit the Earth here at astonishing speed. The Vredefort Dome is what survives of the biggest verified impact structure on the planet, and also one of the oldest. The original crater is estimated to have been around three hundred kilometres across, and erosion has since scraped away most of its form, leaving a ring of low hills about seventy kilometres wide around an uplifted core. UNESCO listed it as a World Heritage Site in 2005, which sounds dry until you stand on the rim and realise that the whole arrangement of rock beneath your tyres was thrown up in minutes.
From the saddle you will not see a crater, and that is part of the point. Vredefort is about understanding rather than seeing. Granite from deep in the crust was pushed to the surface at the centre, and around it the rocks are tilted on end in great arcs. Geologists find shattered cones, a rock fabric that forms only under extreme pressure, and in the landscape the effect is a ring of quartzite ridges around gentle farmland. The Vaal river wanders through the area, and the town of Parys on its banks is the usual base.
The riding here is relaxed and pleasant rather than dramatic. Secondary roads run through maize farms and low koppies, mostly in good condition although with the odd pothole, and traffic is light except at weekends when Johannesburg bikers come out to Parys. The best months are April to June and September to October, when the days are warm and dry, and the veld is golden or fresh green. Summer brings afternoon thunderstorms that can be violent, with hail and lightning.
Parys and Vredefort both sell fuel, and Parys has plenty of cafés and guesthouses, plus a long-standing reputation as an arts town. The area is rich in birdlife, and wildlife includes antelope, and the Vaal draws kayakers and anglers. The gold of the Witwatersrand, which made Johannesburg, lies in rocks that the impact helped to preserve, so the crater is distantly linked to the wealth of the whole country. Pack water, a sun hat and a taste for big skies.