Three-dimensional (3-D) ground-penetrating radar (georadar) mapping offers new opportunities for determining the geometries and facies of surficial sedimentary units. To investigate the potential of this high-resolution technique and at the same time study the architecture of Quaternary glaciofluvial deposits, georadar data have been collected on a dense grid established across a sequence of braided-river gravels and sands in northeastern Switzerland. Results of this survey are striking 3-D images that provide many more details and much more reliable information on the heterogeneities of the shallow underground than are afforded by conventional georadar profile data. Continuous subhorizontal and oblique reflections can be traced throughout vertical sections and horizontal slices of the georadar data block to a depth of (Approx.)15 m. Clearly defined are the dominant flow direction of the ancient braided-river system, the boundaries between different sedimentary facies, and the level of the ground-water table. Trough-fill sediments and subhorizontal channel deposits observed on 7-m-high quarry walls can be followed confidently in the subsurface. The orientation, shape, and size of the troughs and the strike and dip of the cross-bedding are all well resolved.