Sani Pass is at 2065m the highest pass in South Africa. The ride from Underberg to "The highest pub in Africa" is notoriously famous. Mainly because of the very steep and narrow switch banks at the very top. With the fully loaded bike I could cycle up to 2700m from where I had to push for the rest. There is hardly any downhill on the other side but soon the climb to the next pass (Kotisephola Pass 3240m) starts. Fantastic views back down to Underberg and atop you enter another world: no more fences, no trees but open wide plains. A brutal pass to cycle but despite/because of that very cool.
It is certainly worth to continue on through Lesotho after the pass.