Platberg is often known as Harrismith Mountain and is the long mesa east of Harrismith, just over the KZN border in the OFS. There are two tiers of rock. The underlying layer is Cave sandstone. This is soft and not worth climbing. The main, upper, rock layer is steep, fluted dolerite with its characteristic uniform, vertical crack-lines.

In the late 1970s and early 80s many routes were climbed in the NW sector of the mountain. Records of the climbs were collected by a well know climber but were subsequently lost by their guardian - a real microbe !!! - so, all the names, dates and descriptions are now gone forever. Some of the people who were active at this time are Mike Roberts, Steve Cooke and Charl Brummer. Climbing ceased here in about 1983 when a belayer was killed by a falling rock. Reports are that the climbing is generally steep and grades start from about 16 upwards. This area deserves renewed interest.