  In this Chapter we would like to review a "~phenomenological~" approach
taking into account the most fundamental feature of string theory or, more in
general, of quantum gravity, whatever its origin, which is the existence of a
minimal length in the space-time fabric. This length is generally identified
with the Planck length, or the string length, but it could be also much longer
down to the TeV region. A simple and effective way to keep track of the effects
the minimal length in black hole geometries is to solve the Einstein equations
with an energy momentum tensor describing non point-like matter. The immediate
consequence is the absence of any curvature singularity. Where textbook
solutions of the Einstein equations loose any physical meaning because of
infinite tidal forces, we find a de Sitter vacuum core of high, but finite,
energy density and pressure. An additional improvement regards the final stage
of the black hole evaporation leading to a vanishing Hawking temperature even
in the neutral, non-rotating, case. In spite of th simplicity of this model we
are able to describe the final stage of the black hole evaporation, resulting
in a cold remnant with a degenerate, extremal, horizon of radius of the order
of the minimal length. In this chapter we shall describe only neutral,
spherically symmetric, regular black holes although charged, rotating and
higher dimensional black holes can be found in the literature.
