Three problematical features of a karst area developed on the Pre-Cambrian Dolomite Series in the Eastern Transvaal are discussed. It is suggested that the distinctive conical hills to be found along the interfluves are a form of Kegelkarst, despite the fact that dissection is wholly fluvial rather than effected from cockpit evolution. The extensive flat-floored valley basins with steep sides dominated by cones are considered to have evolved through lateral sapping by springs working above an impermeable floor, by floods or by run-off from the steep slopes; they are thus thought to be a type of karst plain. The highly weathered rounded boulder deposits of alluvial origin which occur on I8 m and 30 m terraces are considered to be relict features and to denote a period of intensive chemical weathering following their deposition. Evidence is given that karst processes are no longer active and that the features belong to an earlier cycle of erosion. It is postulated that the conical hills, the flat-floored basins and the rounded boulder deposits are relict landforms developed during active karstification under climatic conditions more humid, if not necessarily warmer, than those operating at present. KARST processes have been invoked to explain surface features in certain areas of the PreCambrian Dolomites of the Transvaal System of South Africa, such as the sinkholes of the western part of the Witwatersrand (A. B. A. Brink and T. C. Partridge, 1965), the Makapan valley (L. C. King, 1951) and the relief in the vicinity of Sterkfontein (C. K. Brain, I958). So far, nothing has been published on the karst topography of that part of the Eastern Transvaal outcrop of the Dolomite Series which is drained by the upper Blyde river (Fig. I). This paper sets out to describe the distinctive conical hills and wide flatfloored valleys to be found in the upper Blyde basin and attempts to explain them in terms of a karst evolution operating at some time in the past. Three particular aspects of the landscape will be considered: the shape and origin of the conical dolomite hills; the form and width of the valleys; and the sedimentary infill of these valleys. Some attempt will be made to date the individual facets of the landscape. The area to be considered in detail measures 24 x 16 km; it is situated 435 km east of Johannesburg on the edge of the plateau zone which terminates in the Great Escarpment, here rising over 900 m above the Lowveld (Fig. 2). Thus the study area is essentially a transition zone between the rolling Highveld at I520830 m and the Lowveld below 600 m and it forms part of the cuesta relief of the Bankenveld (J. Wellington, 1955). The region is one of strong relief ranging from over 1980 m on the dissected plateau in the extreme west to I Ioo m on the valley floor above the falls at the head of the Blyde canyon (Fig. 2). Being in an area of high rainfall (over oo00 mm a year in most parts), the north-flowing Blyde river and its main tributaries are all perennial and the relief is strongly influenced by fluvial dissection, accentuated by the close network of minor streams which flow only in the wet