The compound Ba5I2O12 was synthesized by heating a precipitate of dissolved Ba(OH)2·8H2O and H5IO6. Rb2O was added to increase the crystallite size. The crystal structure was determined from conventional laboratory X-ray diffraction data by using a real-space structure solution approach followed by a Rietveld refinement. No constraints on positions were used. The structure analysis gave an orthorhombic symmetry with a = 19.7474(2) Å, b = 5.9006(1) Å and c = 10.5773(1) Å. The final RBragg value in space group Pnma (62) was 1.0 %. The structure can be described by layers of a metal and iodine arrangement forming almost pentagonal holes. Raman measurements were correlated with the two IO6 octahedra. Two further barium periodate patterns were observed and indexed.