  We point out that the moduli sector of the $(2,2)$ string compactification
with its nonperturbatively preserved non-compact symmetries is a framework to
study global topological defects. Based on the target space modular invariance
of the nonperturbative superpotential of the four-dimensional $N=1$
supersymmetric string vacua, topologically stable stringy domain walls are
found. Explicit supersymmetric solutions for the modulus field and the metric,
which saturate the Bogomol'nyi bound, are presented. They interpolate between
{\it non-degenerate} vacua. As a corollary, this defines a new notion of vacuum
degeneracy of supersymmetric vacua. Nonsupersymmetric stringy domain walls are
discussed as well. The moduli sectors with more than one modulus and the
non-compact continous symmetry preserved allow for global monopole-type and
texture-type configurations.
