Single crystals of the nanoscale polyoxomolybdate wheel, Na(15)Fe(3)Co(16)[Mo(176)O(528)(H(2)O)(80)]Cl(27) x 450 H(2)O, was synthesized by the condensation reaction of Na(0.4)Co(0.8)[MoO(4)] x 1.5 H(2)O at low pH and in the presence of an iron-based reducing agent, and these crystals were characterized by the synchrotron-based X-ray single crystal analysis, magnetic susceptibility, and ionic conductivity measurements.