Globular Clusters are the best approximations to simple stellar
populations known to exist. Compared to the complex stellar population
mix of the diffuse (i.e. unresolved) light of their host galaxies, the
integrated light of globular clusters can be reliably compared to
population synthesis model predictions. Given that globular clusters
exist in virtually every galaxy and form during major star formation
episodes, they can be used as tracer populations of star formation and
assembly histories of their host galaxies. In my talk, I will
recapitulate evidence for the presence of multiple globular cluster
sub-populations in the Local Group. Moving on to more massive systems,
I will also present recent advance in modeling the chemical
composition distributions of globular cluster systems in massive
elliptical galaxies that appear to be consistent with the monolithic
collapse formation scenario. The comparison of model predictions with
spectroscopic observations reveals the presence of a new, super
metal-rich globular cluster population that is likely to exist only in
the most massive galaxies. Furthermore, there is strong evidence for
multiple enrichment epochs/mechanisms of the ancient globular cluster
sub-population, the formation of which likely predates the formation
epoch of the vast majority of stars in elliptical galaxies. I will
discuss these results, in particular in the context of hierarchical
galaxy formation.