A hundred and fifty kilometres from Johannesburg, the ground rises into a ring of low hills about seventy kilometres across, and that ring is the surviving core of the largest meteorite impact the Earth has kept a record of. Vredefort Dome formed about two billion years ago, when an asteroid several kilometres wide hit what was then a very different landscape. The structure was once perhaps three hundred kilometres across, and erosion since has scraped most of it away, leaving the central uplift visible. UNESCO listed it in 2005.
On the ground the effect is gentle and slightly confusing. There is no crater to stand at the edge of. Instead you ride across a landscape of granite domes and ridges, with the concentric hills of the collar rock rising around you, and the geology is knowledge more than view. Look for the steeply tilted layers in the ridges, which were flipped upright by the impact, and for the shatter cones, striated pieces of rock that formed in the shock wave. The nearby Vaal River curls around the north of the dome, and Parys, a pleasant little town on its bank, is popular with weekenders.
The roads suit a relaxed ride. Tarmac is generally good, with wide bends and long straights through farmland, and the gravel back roads are fine on a dual-sport bike when dry. Watch for stock on the road and for trucks on the main routes. Summer thunderstorms are fierce, and winter nights are cold enough for frost.
Vredefort, the small town after which the dome is named, is about twenty kilometres away and has a few services. Parys has more shops, places to eat and fuel, and Potchefstroom is bigger still. If you want to learn more about the science, try to arrange a visit with a local guide, because the best features are on private farms and are easy to miss. The light is excellent in the early morning and late afternoon.