  We calculate the energies of various multiple-spiral spin configurations for
the three-dimensional model of chiral magnets. The ground-state phase diagram
is obtained in the space of anisotropy, magnetic field, and interaction
parameters. Regimes with multiple-spiral, or spin crystal ground states of two-
and three-dimensional nature are identified. The Skyrmion number responsible
for anomalous Hall effect is examined for each spin crystal configuration. A
geometric interpretation is given for the three-dimensional spin crystal
lattice structures as the periodic arrangement of hedgehog and anti-hedgehog
singularities.
