The Vredefort Dome, where Forest Run is held (in a part of the area – the best part IMHO) is a UNESCO World Heritage site. Curious about what they have to say about the area, I found their website.
“The Vredefort Dome is 120 km south west from Johannesburg. The property represents a unique geological phenomenon formed about 2 023 million years ago and is the oldest and largest known meteorite impact structure on earth.”
Check it out the Vredefort Dome on the UNESCO World Heritage List.