The authors show that if D is a convex polyhedron (of unknown shape) inside a electrically conductive domain \(\Omega \subset {\mathbb{R}}^ n\), \(n\geq 2\), then its exact location can be determined by a single experiment, consisting in the application of a current across the boundary \(\partial \Omega\) and the measurement of the voltage u on a part \(\Gamma_ 0\) of \(\partial \Omega\), which is the solution of an associated refraction problem in \(\Omega\).