The reaction of 2-pyridylphosphonic acid (LH2) with iron(II) perchlorate and iron(III) nitrate afforded an interconnected, double-layered, cationic iron cage, [{Fe36L44(H2O)(48)}](20+) (1a), the largest interconnected, polynuclear ferric cage reported to date. Magnetic studies on la revealed antiferromagnetic coupling between the spins on adjacent Fe-III ions.