  We report on the complex structure of the red giant branch (RGB) of omega
Cen, based on a new wide field and wide color baseline B and I photometry. Our
color magnitude diagram (CMD) shows the presence of multiple populations along
this branch, in particular we discovered an anomalous branch (RGB-a), which
appears to be well separated from the bulk of the RGB stars. On the basis of
our CMD and from the previous literature we conclude that (1) these stars,
clearly identified as a separate population in our CMD, represent the extreme
metal rich extension ([Ca/H]>-0.3) of the stellar content of omega Cen, and
show anomalous abundances of s-process elements (as Ba and Zr) as well; (2)
they are physical members of the omega Cen system; (3) they comprise ~ 5% of
the stars of the whole system; (4) this component and the metal-intermediate
one (-0.4>[Ca/H]>-1) have been found to share the same spatial distribution,
both of them differing significantly from the most metal poor one ([Ca/H]<-1).
This last evidence supports the hypothesis that metal rich components could
belong to an independent (proto?) stellar system captured in the past by omega
Cen.
