  Let Gamma\D be an arithmetic quotient of a symmetric space of non-compact
type. A spine D_0 is a Gamma-equivariant deformation retraction of D with
dimension equal to the virtual cohomological dimension of Gamma. We explicitly
construct a spine for the case of Gamma=SU(2,1;Z[i]). The spine is then used to
compute the cohomology of Gamma\D with various local coefficients.
