We report the synthesis, structure determination, and structure analysis of La18W10O57, which presents 52.65 WO3 mol % in the binary system La2O3-WO3 in place of the previous reported compound: La14W8O45, 53.3 WO3 Mol %, The structure has been determined from synchrotron and laboratory X-ray, neutron, and electron diffraction data, This tungstate crystallizes in the non-centrosymmetric hexagonal space group (no. 190) P (6) over bar 2c, with Z = 2, a = 9.0448(1) angstrom, c = 32.6846(3) angstrom, and a measured density of 7.28(3) g.cm(-3). The structure consists of [WO6] octahedra, isolated or sometimes sharing a face, and unusual tungsten [WO6] trigonal prisms. This compound presents a subcell c' = c/6 = 5.45 angstrom. Polytypism has been observed concerning this compound. Transmission electronic microscopy, ionic conductivity, and thermal expansion have been explored.