  Profiles of static solitons in one-dimensional scalar field theory satisfy
the same equations as trajectories of a fictitious particle in multidimensional
mechanics. We argue that the structure and properties of the solitons are
essentially different if the respective mechanical motions are chaotic. This
happens in multifield models and models with spatially dependent potential. We
illustrate our findings using one-field sine-Gordon model in external Dirac
comb potential. First, we show that the number of different "chaotic" solitons
grows exponentially with their length, and the growth rate is related to the
topological entropy of the mechanical system. Second, the field values of
stable solitons form a fractal; we compute its box-counting dimension. Third,
we demonstrate that the distribution of field values in the fractal is related
to the metric entropy of the analogous mechanical system.
