  We derive a class of solutions to the string sigma-model equations for the
closed bosonic string. The tachyon field is taken to form a constant condensate
and the beta-function equations at one-loop level are solved for the evolution
of the metric and the dilaton. The solutions represent critical string theories
in arbitrary dimensions. The spectrum of the subclass of models with a linearly
rising asymptotic dilaton is found using the Feigin-Fuks method. Certain
approximate solutions arising in string field theory are used to illustrate the
results explicitly. An argument based on conformal invariance leads to the
conjecture that that stringy corrections to at least some singular spacetimes
in general relativity result in non-singular metrics. We use the singularities
of the big-bang/crunch type appearing in our models to examine this conjecture.
