  We show that the geometrically-induced potential existing in undulated slab
waveguides dramatically affects the properties of solitons. In particular,
whereas solitons residing in the potential maxima do not feature power
thresholds and are stable, their counterparts residing in the potential minima
are unstable and may exhibit a power threshold for their existence.
Additionally, the geometric potential is shown to supports stable multipole
solitons that cannot be supported by straight waveguides. Finally, the
geometric potential results in the appearance of the effective barriers that
prevent transverse soliton motion.
