  We present qualitative evidence that closed string tachyon solitons describe
backgrounds of lower-dimensional sub-critical string theory. We show that a
co-dimension one soliton in the low energy effective gravity-dilaton-tachyon
theory in general has a flat string-frame metric, and a dilaton that grows in
both directions away from the core, and is linear in the soliton worldvolume
coordinates. Spacetime, as seen in the Einstein frame, is therefore effectively
localized in (D-1)-dimensions, in which the dilaton is linear, in agreement
with the linear dilaton background of the (D-1)-dimensional sub-critical
string. We construct a number of exactly solvable toy models with specific
tachyon potentials that exhibit these features, and address the question of
finding solitons in the bosonic closed string field theory using the recent
advances in computing the tachyon potential.
