  Each of the four critical Severi varieties arises from a minimal holomorphic
nilpotent orbit in a simple regular rank 3 hermitian Lie algebra and each such
variety lies as singular locus in a cubic--the chordal variety--in the
corresponding complex projective space; the cubic and projective space are
identified in terms of holomorphic nilpotent orbits. The projective space
acquires an exotic K\"ahler structure with three strata, the cubic is an
example of an exotic projective variety with two strata, and the corresponding
Severi variety is the closed stratum in the exotic variety as well as in the
exotic projective space. In the standard cases, these varieties arise also via
K\"ahler reduction. An interpretation in terms of constrained mechanical
systems is included.
