  Supersymmetric closed string theories contain an infinite tower of
BPS-saturated, oscillating, macroscopic strings in the perturbative spectrum.
When these theories have dual formulations, this tower of states must exist
nonperturbatively as solitons in the dual theories. We present a general class
of exact solutions of low-energy supergravity that corresponds to all these
states. After dimensional reduction they can be interpreted as supersymmetric
black holes with a degeneracy related to the degeneracy of the string states.
{}For example, in four dimensions we obtain a point-like solution which is
asymptotic to a stationary, rotating, electrically-charged black hole with
Regge-bounded angular momentum and with the usual ring-singularity replaced by
a string source. This further supports the idea that the entropy of
supersymmetric black holes can be understood in terms of counting of string
states. We also discuss some applications of these solutions to string duality.
