  We report on results of systematic numerical studies of two-dimensional
electron gas systems subject to a perpendicular magnetic field, with a high
Landau level partially filled by electrons. Our results are strongly suggestive
of a breakdown of translational symmetry and the presence of crystalline order
in the ground state. This is in sharp contrast with the physics of the lowest
and first excited Landau levels, and in good qualitative agreement with earlier
Hartree-Fock studies. Experimental implications of our results are discussed.
