  In June 2005 the PHOBOS Collaboration completed data taking at RHIC. In five
years of operation PHOBOS recorded information for Au+Au at $\sqrt{s_{NN}}$ =
19.6, 62.4, 130, and 200 GeV, Cu+Cu at 22.4, 62.4 and 200 GeV, d+Au at 201 GeV,
and p+p at 200 and 410 GeV, altogether more than one billion collisions. Using
these data we have studied the energy and centrality dependence of the global
properties of charged particle production over essentially the full 4$\pi$
solid angle and (for pions near mid rapidity) charged particle spectra down to
transverse momenta below 30 MeV/c. We have also studied correlations of
particles separated in pseudorapidity by up to 6 units. We find that the global
properties of heavy ion collisions can be described in terms of a small number
of simple dependencies on energy and centrality, and that there are strong
correlations between the produced particles. To date no single model has been
proposed which describes this rich phenomenology. In this talk I summarize what
the data is explicitly telling us.
