  We present a cosmological zoom-in simulation of a Milky Way-like galaxy used
to explore the formation and evolution of star clusters. We investigate in
particular the origin of the bimodality observed in the colour and metallicity
of globular clusters, and the environmental evolution through cosmic times in
the form of tidal tensors. Our results self-consistently confirm previous
findings that the blue, metal-poor clusters form in satellite galaxies which
are accreted onto the Milky Way, while the red, metal-rich clusters form mostly
in situ or, to a lower extent in massive, self-enriched galaxies merging with
the Milky Way. By monitoring the tidal fields these populations experience, we
find that clusters formed in situ (generally centrally concentrated) feel
significantly stronger tides than the accreted ones, both in the present-day,
and when averaged over their entire life. Furthermore, we note that the tidal
field experienced by Milky Way clusters is significantly weaker in the past
than at present-day, confirming that it is unlikely that a power-law cluster
initial mass function like that of young massive clusters, is transformed into
the observed peaked distribution in the Milky Way with relaxation-driven
evaporation in a tidal field.
