  We investigate the geometry of four dimensional black hole solutions in the
presence of stringy higher curvature corrections to the low energy effective
action. For certain supersymmetric two charge black holes these corrections
drastically alter the causal structure of the solution, converting seemingly
pathological null singularities into timelike singularities hidden behind a
finite area horizon. We establish, analytically and numerically, that the
string-corrected two-charge black hole metric has the same Penrose diagram as
the extremal four-charge black hole. The higher derivative terms lead to
another dramatic effect -- the gravitational force exerted by a black hole on
an inertial observer is no longer purely attractive! The magnitude of this
effect is related to the size of the compactification manifold.
