  We uplift the static three dimensional black hole solution found by Banados,
Teitelboim and Zanelli (BTZ) into four dimensional space time. In this way we
obtain a black string solution with a relativistic string source, as well as a
new black hole solution which is also generated by a relativistic ``stringy''
source. It is shown that when passing continuously from the region of the one
dimensional parameter spaces which characterize these solutions, containing
naked singular strings or naked singular ``points'', and into the region
containing black strings or black holes, the metrics ``blow up'' at a critical
point in both parameter spaces. We show that a similar ``separation'' mechanism
can be introduced in three dimensions. In this way we also obtain a
generalization of the BTZ solution. The ``separation'' mechanism, and its
immediate consequences, offers an hitherto missing technical argument needed in
order to exclude the naked singularities (the ``mass gap'') from the space of
``physically permissible'' solutions in three dimensional Einstein theory
coupled to a negative cosmological constant.
  PACS nos.: 04.40.Nr, 04.20.Cv
