  Many cosmological observations call for the existence of dark matter. The
most direct evidence for dark matter is inferred from the measured flatness of
galactic rotation curves. The latter is based on Newtonian gravity. Alternative
approaches to the rotation curve problem by means of general relativity have
recently been put forward. The class of models of interest is a subset of the
axially symmetric and stationary solutions of Einstein's equations with
rotating dust. As a step toward the understanding of general relativistic
galaxy models, we analyse rigidly as well as non-rigidly rotating
(Post-)Newtonian spacetimes. We find that the Newtonian limit of the considered
general relativistic galaxy model leads to Post-Newtonian terms in the metric.
