  We report on magnetotransport of a two-dimensional electron system (2DES),
located 32 nm below the surface, with a surface superlattice gate structure of
periodicity 39 nm imposing a periodic modulation of its potential. For low
Landau level fillings $\nu$, the diagonal resistivity displays a rich pattern
of fluctuations, even though the disorder dominates over the periodic
modulation. Theoretical arguments based on the combined effects of the
long-wavelength, strong disorder and the short-wavelength, weak periodic
modulation present in the 2DES qualitatively explain the data.
