A brief review is given of the use of duality symmetries to form orbits of supergravity black-hole solutions and their relation to extremal (i.e. BPS) solutions at the limits of such orbits. An important technique in this analysis uses a timelike dimensional reduction and exchanges the stationary black-hole problem for a nonlinear sigma-model problem. Families of BPS solutions are characterized by nilpotent orbits under the duality symmetries, based upon a tri-graded or pentagraded decomposition of the corresponding duality group algebra.Aside from the general mathematical interest in classifying black hole solutions of any kind, the study of families of such solutions is also of current interest because it touches other important issues in theoretical physics. For example, the classification of BPS and non-BPS black holes forms part of a more general study of branes in supergravity and superstring theory. Branes and their intersections, as well as their worldvolume modes and attached string modes, are key elements in phenomenological approaches to the marriage of string theory with particle physics phenomenology. The related study of nonsingular and horizon-free BPS gravitational solitons is also central to the "fuzzball" proposal of BPS solutions as candidate black-hole quantum microstates.The search for supergravity solutions with assumed Killing symmetries can be recast as a Kaluza-Klein problem [1,2,3]. To see this, consider a 4D theory with a nonlinear bosonic symmetry G 4 (e.g. the "duality" symmetry E 7 for maximal N = 8 supergravity). Scalar fields take their values in a target space Φ 4 = G 4 /H 4 , where H 4 is the corresponding linearly realized subgroup, generally the maximal compact subgroup of G 4 (e.g. SU(8) ⊂ E 7 for N = 8 SG). The search will be constrained by the following considerations:• We assume that a solution spacetime is asymptotically flat or asymptotically Taub-NUT and that there is a 'radial' function r which is divergent in the asymptotic region, g µν ∂ µ r∂ ν r ∼ 1 + O(r −1 ).• Searching for stationary solutions amounts to assuming that a solution possesses a timelike Killing vector field κ µ (x). Lie derivatives with respect to κ µ are assumed to vanish on all fields. The Killing vector κ µ will be assumed to have 1