I started regular mountain biking after a long break about 2 years ago; and have largely stuck to Groenkloof Nature Reserve just outside Pretoria. Groenkloof has a lot of variety in terms of length and difficulty of tracks; and over the past two years, I have steadily increased both the distance and difficulty of my rides.
In the past few weeks, I have branched out to other venues - Modderfontein reserve, and Northern Farm. Both venues are more well known, and more popular; but strangely much of their tracks are relatively easy in terms of difficulty. In fact, except for some sandy trails, there isn't much in terms of difficult terrain (both venues seem to focus more on distance it seems) - at least on the intermediate rated tracks I have ridden.
While neither has the large game that roam Groenkloof (so no running into giraffes, zebras and ostriches), the do compensate with more dams and greenery. In fact, Modderfontein dam spots a neat waterfall near the entrance of the trail (and the view from the Gautrain as it approaches Marlboro station in the mornings can be spectacular).
I will keep riding on Groenkloof for most weeks - the uphills and terrain may be more painful; but equally their downhills are faster and more exhilarating; and it ultimately provides more exercise. Northern Farm and Modderfontein can serve as nice breaks in routine however - and I am keen to explore other opportunities for more such breaks.
