Near the village of Duurwater Pos at the foot of the Fransfontein Ridge, north-western Namibia, an erratic megalith of basement monzogranite (Huab gneiss), 130 m long by 52 m wide, is perched on a pedestal of early Cryogenian (Sturtian) tillite. The pedestal had at least 134 m of palaeotopographic relief, plus the additional 41 m (tilt-corrected) height of the erratic itself. The tillite pedestal is inferred to be a hoodoo structure formed by differential erosion with shielding of the pedestal by the hard basement erratic. The erratic and its pedestal were preserved because of rapid marine inundation during Snowball Earth deglaciation, followed by onlap and burial by postglacial carbonate sediments of the middle Cryogenian Berg Aukas and Okonguarri Formations. As a glacial erratic, it is possibly the largest and oldest example known. Keywords: Glacial erratic, Cryogenian, Chuos glaciation, Snowball Earth, Fransfontein Ridge.