Reduction of an acidified solution of Na2MoO4·2H2O by iron powder results in the formation of the title compound [Mo176O16O480(OH)32(H2O)80]; the compound is tyre shaped and consists of sixteen {Mo8} subunits being linked by forty-eight MoO6 octahedra; remarkable features are the size and mass (which is of the order of a protein) and its nanodimensional cavity of ca. 3 nm in diameter.