We report the first example of a polynuclear discrete coordination compound exhibiting only bpym bridges and containing a first-row d transition metal. A smooth self-assembly one-pot synthetic route, starting from simply FeCl2 and FeCl3 hydrates, allowed us to prepare a tetranuclear Fe-4 cluster with a stairway-like structure and the formula cis-{[(H2O)Cl3FeIII-mu(bpym)(FeCl2)-Cl-II]}(2)-mu(bpym) (1). All spectroscopic data suggest that complex 1 is a valencelocalized mixed-valent Fe-II-Fe-III cluster with typical Mossbauer lines for both sites, which do not change with temperature. Reflectance spectroscopy did not allow one to distinguish an intervalence charge-transfer band. However, time-dependent density functional theory (DFT) calculations predict a weak high-energy Fe-II -> Fe-III transition. Regarding the magnetic properties, the high-spin Fe-II and Fe-III ions interact in a weakly antiferromagnetic way with isotropic J constants of only a few wavenumbers as derived from direct-current susceptibility and magnetization data. Broken-symmetry DFT calculations support these observations.