  Taking the flat rotation curve as input and treating the matter content in
the galactic halo region as perfect fluid, we obtain space time metric at the
galactic halo region in the framework of general relativity. We find that the
resultant metric is a non-relativistic-dark-matter-induced space-time embedded
in a static Friedmann-Lema\^itre-Robertson-Walker universe. This means that the
flat rotation curve not only leads to the existence of dark matter but also
suggests the background geometry of the universe. The flat rotation curve and
the demand that the dark matter be non-exotic together indicate a (nearly) flat
universe as favored by the modern cosmological observations. We obtain the
expressions for energy density and pressure of dark matter halo and
consequently the equation of state of dark matter. Various other aspects of the
solution are also analyzed.
