  A brief overview of strings propagating on noncompact coset spaces G/H is
presented in terms of WZW models. The role played by isometries in the
existence of target space duality and by fixed points of the gauge
transformations in the existence of singularities and horizons, is emphasized.
A general classification of the spaces with a single time-like coordinate is
presented. The spacetime geometry of a class of models, existing for every
dimension and having cosmological and black hole-like interpretations, is
discussed.
